diff --git a/.gitignore b/.gitignore
index 6240d7d..283b0ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,7 @@ dist/
 .DS_Store
 .vscode/
 .idea/
+.copilot-project-context.md
 
 # Generated outputs
 *.ppm
diff --git a/Makefile b/Makefile
index d54c76f..624ba14 100644
--- a/Makefile
+++ b/Makefile
@@ -3,13 +3,12 @@
 # Unstructured data visualization tool
 
 CC = gcc
-CFLAGS = -Wall -Wextra -O2 -g
+CFLAGS = -Wall -Wextra -O2 -g -fopenmp
 # --enable-new-dtags is Linux-only, skip on macOS (Darwin)
 UNAME_S := $(shell uname -s)
-ifneq ($(UNAME_S),Darwin)
-LDFLAGS = -Wl,--enable-new-dtags
-else
-LDFLAGS =
+LDFLAGS = -fopenmp
+ifeq ($(UNAME_S),Darwin)
+LDFLAGS += -Wl,--enable-new-dtags
 endif
 
 # NetCDF - try DKRZ system installation first, fall back to system nc-config
@@ -71,7 +70,7 @@ endif
 BASE_CFLAGS = $(CFLAGS) $(NETCDF_CFLAGS)
 X11_FULL_CFLAGS = $(X11_CFLAGS) $(BASE_CFLAGS)
 
-COMMON_LIBS = $(NETCDF_LIBS) $(NETCDF_RPATH) -lm
+COMMON_LIBS = $(NETCDF_LIBS) $(NETCDF_RPATH) -lm -lpthread
 USHOW_LIBS = $(COMMON_LIBS) $(X11_LIBS) $(X11_RPATH)
 UTERM_LIBS = $(COMMON_LIBS)
 
@@ -179,7 +178,8 @@ SRCDIR = src
 OBJDIR = obj
 BINDIR = .
 
-COMMON_SRCS = $(SRCDIR)/kdtree.c \
+COMMON_SRCS = $(SRCDIR)/common.c \
+              $(SRCDIR)/kdtree.c \
               $(SRCDIR)/mesh.c \
               $(SRCDIR)/regrid.c \
               $(SRCDIR)/projection.c \
@@ -263,29 +263,29 @@ clean:
 	rm -f uterm
 
 # Dependencies
-$(OBJDIR)/ushow.o: $(SRCDIR)/ushow.c $(SRCDIR)/ushow.defines.h $(SRCDIR)/mesh.h \
+$(OBJDIR)/ushow.o: $(SRCDIR)/ushow.c $(SRCDIR)/us_types.h $(SRCDIR)/mesh.h \
                    $(SRCDIR)/regrid.h $(SRCDIR)/file_netcdf.h $(SRCDIR)/colormaps.h \
                    $(SRCDIR)/view.h $(SRCDIR)/interface/x_interface.h
-$(OBJDIR)/uterm.o: $(SRCDIR)/uterm.c $(SRCDIR)/ushow.defines.h $(SRCDIR)/mesh.h \
+$(OBJDIR)/uterm.o: $(SRCDIR)/uterm.c $(SRCDIR)/us_types.h $(SRCDIR)/mesh.h \
                    $(SRCDIR)/regrid.h $(SRCDIR)/file_netcdf.h $(SRCDIR)/colormaps.h \
                    $(SRCDIR)/term_render_mode.h \
                    $(SRCDIR)/view.h
 $(OBJDIR)/term_render_mode.o: $(SRCDIR)/term_render_mode.c $(SRCDIR)/term_render_mode.h
 $(OBJDIR)/kdtree.o: $(SRCDIR)/kdtree.c $(SRCDIR)/kdtree.h
-$(OBJDIR)/mesh.o: $(SRCDIR)/mesh.c $(SRCDIR)/mesh.h $(SRCDIR)/ushow.defines.h
+$(OBJDIR)/mesh.o: $(SRCDIR)/mesh.c $(SRCDIR)/mesh.h $(SRCDIR)/us_types.h
 $(OBJDIR)/regrid.o: $(SRCDIR)/regrid.c $(SRCDIR)/regrid.h $(SRCDIR)/mesh.h \
-                    $(SRCDIR)/kdtree.h $(SRCDIR)/projection.h $(SRCDIR)/ushow.defines.h
-$(OBJDIR)/projection.o: $(SRCDIR)/projection.c $(SRCDIR)/projection.h $(SRCDIR)/ushow.defines.h
-$(OBJDIR)/file_netcdf.o: $(SRCDIR)/file_netcdf.c $(SRCDIR)/file_netcdf.h $(SRCDIR)/ushow.defines.h
-$(OBJDIR)/file_mitgcm.o: $(SRCDIR)/file_mitgcm.c $(SRCDIR)/file_mitgcm.h $(SRCDIR)/mesh.h $(SRCDIR)/ushow.defines.h
-$(OBJDIR)/colormaps.o: $(SRCDIR)/colormaps.c $(SRCDIR)/colormaps.h $(SRCDIR)/ushow.defines.h
+                    $(SRCDIR)/kdtree.h $(SRCDIR)/projection.h $(SRCDIR)/us_types.h
+$(OBJDIR)/projection.o: $(SRCDIR)/projection.c $(SRCDIR)/projection.h $(SRCDIR)/us_types.h
+$(OBJDIR)/file_netcdf.o: $(SRCDIR)/file_netcdf.c $(SRCDIR)/file_netcdf.h $(SRCDIR)/us_types.h
+$(OBJDIR)/file_mitgcm.o: $(SRCDIR)/file_mitgcm.c $(SRCDIR)/file_mitgcm.h $(SRCDIR)/mesh.h $(SRCDIR)/us_types.h
+$(OBJDIR)/colormaps.o: $(SRCDIR)/colormaps.c $(SRCDIR)/colormaps.h $(SRCDIR)/us_types.h
 $(OBJDIR)/view.o: $(SRCDIR)/view.c $(SRCDIR)/view.h $(SRCDIR)/file_netcdf.h \
-                  $(SRCDIR)/regrid.h $(SRCDIR)/colormaps.h $(SRCDIR)/ushow.defines.h
+                  $(SRCDIR)/regrid.h $(SRCDIR)/colormaps.h $(SRCDIR)/us_types.h
 $(OBJDIR)/interface/x_interface.o: $(SRCDIR)/interface/x_interface.c \
                                     $(SRCDIR)/interface/x_interface.h \
                                     $(SRCDIR)/interface/colorbar.h \
                                     $(SRCDIR)/interface/timeseries_popup.h \
-                                    $(SRCDIR)/ushow.defines.h
+                                    $(SRCDIR)/us_types.h
 $(OBJDIR)/interface/colorbar.o: $(SRCDIR)/interface/colorbar.c \
                                  $(SRCDIR)/interface/colorbar.h $(SRCDIR)/colormaps.h
 $(OBJDIR)/interface/range_popup.o: $(SRCDIR)/interface/range_popup.c \
@@ -295,25 +295,25 @@ $(OBJDIR)/interface/range_utils.o: $(SRCDIR)/interface/range_utils.c \
                                     $(SRCDIR)/interface/range_utils.h
 $(OBJDIR)/interface/timeseries_popup.o: $(SRCDIR)/interface/timeseries_popup.c \
                                          $(SRCDIR)/interface/timeseries_popup.h \
-                                         $(SRCDIR)/ushow.defines.h
+                                         $(SRCDIR)/us_types.h
 
 # Zarr dependencies (when WITH_ZARR is set)
 ifdef WITH_ZARR
-$(OBJDIR)/file_zarr.o: $(SRCDIR)/file_zarr.c $(SRCDIR)/file_zarr.h $(SRCDIR)/ushow.defines.h \
+$(OBJDIR)/file_zarr.o: $(SRCDIR)/file_zarr.c $(SRCDIR)/file_zarr.h $(SRCDIR)/us_types.h \
                         $(SRCDIR)/cJSON/cJSON.h
 $(OBJDIR)/cJSON/cJSON.o: $(SRCDIR)/cJSON/cJSON.c $(SRCDIR)/cJSON/cJSON.h
 endif
 
 # GRIB dependencies (when WITH_GRIB is set)
 ifdef WITH_GRIB
-$(OBJDIR)/file_grib.o: $(SRCDIR)/file_grib.c $(SRCDIR)/file_grib.h $(SRCDIR)/ushow.defines.h
+$(OBJDIR)/file_grib.o: $(SRCDIR)/file_grib.c $(SRCDIR)/file_grib.h $(SRCDIR)/us_types.h
 endif
 
 # YAC dependencies (when WITH_YAC is set)
 ifdef WITH_YAC
 $(OBJDIR)/regrid_yac.o: $(SRCDIR)/regrid_yac.c $(SRCDIR)/regrid_yac.h \
-                         $(SRCDIR)/healpix.h $(SRCDIR)/mesh.h $(SRCDIR)/ushow.defines.h
-$(OBJDIR)/healpix.o: $(SRCDIR)/healpix.c $(SRCDIR)/healpix.h $(SRCDIR)/ushow.defines.h
+                         $(SRCDIR)/healpix.h $(SRCDIR)/mesh.h $(SRCDIR)/us_types.h
+$(OBJDIR)/healpix.o: $(SRCDIR)/healpix.c $(SRCDIR)/healpix.h $(SRCDIR)/us_types.h
 endif
 
 # Print configuration
diff --git a/src/colormaps.h b/src/colormaps.h
index 07ca5c9..9bceacd 100644
--- a/src/colormaps.h
+++ b/src/colormaps.h
@@ -5,7 +5,7 @@
 #ifndef COLORMAPS_H
 #define COLORMAPS_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Initialize colormaps (load built-in colormaps).
diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..75bc4da
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,134 @@
+/*
+ * common.c - Shared utilities for ushow and uterm
+ */
+
+#include "common.h"
+#include "kdtree.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#ifdef _OPENMP
+#include <omp.h>
+#endif
+
+#define DEFAULT_THREADS 4
+
+void apply_thread_settings(int user_threads) {
+    if (user_threads > 0) {
+        kdtree_set_max_threads(user_threads);
+#ifdef _OPENMP
+        omp_set_num_threads(user_threads);
+#endif
+    } else if (!getenv("OMP_NUM_THREADS")) {
+#ifdef _OPENMP
+        omp_set_num_threads(DEFAULT_THREADS);
+#endif
+    }
+}
+
+int parse_time_units(const char *units, double *unit_seconds,
+                     int *y, int *mo, int *d, int *h, int *mi, double *sec) {
+    if (!units || !unit_seconds || !y || !mo || !d || !h || !mi || !sec) return 0;
+
+    const char *since = strstr(units, "since");
+    if (!since) return 0;
+
+    char unit_buf[32] = {0};
+    if (sscanf(units, "%31s", unit_buf) != 1) return 0;
+
+    /* Normalize unit token to lower case */
+    for (char *p = unit_buf; *p; ++p) {
+        if (*p >= 'A' && *p <= 'Z') *p = (char)(*p - 'A' + 'a');
+    }
+
+    if (strcmp(unit_buf, "seconds") == 0 || strcmp(unit_buf, "second") == 0 ||
+        strcmp(unit_buf, "secs") == 0 || strcmp(unit_buf, "sec") == 0 || strcmp(unit_buf, "s") == 0) {
+        *unit_seconds = 1.0;
+    } else if (strcmp(unit_buf, "minutes") == 0 || strcmp(unit_buf, "minute") == 0 ||
+               strcmp(unit_buf, "mins") == 0 || strcmp(unit_buf, "min") == 0) {
+        *unit_seconds = 60.0;
+    } else if (strcmp(unit_buf, "hours") == 0 || strcmp(unit_buf, "hour") == 0 ||
+               strcmp(unit_buf, "hrs") == 0 || strcmp(unit_buf, "hr") == 0) {
+        *unit_seconds = 3600.0;
+    } else if (strcmp(unit_buf, "days") == 0 || strcmp(unit_buf, "day") == 0) {
+        *unit_seconds = 86400.0;
+    } else {
+        return 0;
+    }
+
+    /* Parse origin date/time after "since" */
+    const char *p = since + 5;
+    while (*p == ' ') p++;
+    int n = sscanf(p, "%d-%d-%d %d:%d:%lf", y, mo, d, h, mi, sec);
+    if (n < 3) return 0;
+    if (n == 3) { *h = 0; *mi = 0; *sec = 0.0; }
+    return 1;
+}
+
+int64_t days_from_civil(int y, unsigned m, unsigned d) {
+    y -= m <= 2;
+    const int era = (y >= 0 ? y : y - 399) / 400;
+    const unsigned yoe = (unsigned)(y - era * 400);
+    const unsigned doy = (153 * (m + (m > 2 ? -3 : 9)) + 2) / 5 + d - 1;
+    const unsigned doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;
+    return (int64_t)(era * 146097 + (int)doe - 719468);
+}
+
+void civil_from_days(int64_t z, int *y, unsigned *m, unsigned *d) {
+    z += 719468;
+    const int era = (z >= 0 ? z : z - 146096) / 146097;
+    const unsigned doe = (unsigned)(z - era * 146097);
+    const unsigned yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
+    int y_tmp = (int)(yoe) + era * 400;
+    const unsigned doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
+    const unsigned mp = (5 * doy + 2) / 153;
+    const unsigned d_tmp = doy - (153 * mp + 2) / 5 + 1;
+    const unsigned m_tmp = mp + (mp < 10 ? 3 : -9);
+    y_tmp += (m_tmp <= 2);
+
+    *y = y_tmp;
+    *m = m_tmp;
+    *d = d_tmp;
+}
+
+int format_time_from_units(char *out, size_t outlen, double value, const char *units) {
+    if (!out || outlen == 0) return 0;
+
+    double unit_seconds = 0.0;
+    int y, mo, d, h, mi;
+    double sec;
+    if (!parse_time_units(units, &unit_seconds, &y, &mo, &d, &h, &mi, &sec)) {
+        return 0;
+    }
+
+    int64_t days = days_from_civil(y, (unsigned)mo, (unsigned)d);
+    double total_sec = (double)days * 86400.0 + (double)h * 3600.0 + (double)mi * 60.0 + sec;
+    total_sec += value * unit_seconds;
+
+    int64_t out_days = (int64_t)(total_sec / 86400.0);
+    double rem = total_sec - (double)out_days * 86400.0;
+    if (rem < 0) {
+        rem += 86400.0;
+        out_days -= 1;
+    }
+
+    int out_y;
+    unsigned out_m, out_d;
+    civil_from_days(out_days, &out_y, &out_m, &out_d);
+
+    int out_h = (int)(rem / 3600.0);
+    rem -= out_h * 3600.0;
+    int out_mi = (int)(rem / 60.0);
+    rem -= out_mi * 60.0;
+    int out_s = (int)(rem + 0.5);
+
+    if (out_h == 0 && out_mi == 0 && out_s == 0) {
+        snprintf(out, outlen, "%04d-%02u-%02u", out_y, out_m, out_d);
+    } else {
+        snprintf(out, outlen, "%04d-%02u-%02u %02d:%02d:%02d",
+                 out_y, out_m, out_d, out_h, out_mi, out_s);
+    }
+    return 1;
+}
diff --git a/src/common.h b/src/common.h
new file mode 100644
index 0000000..8c0e3cc
--- /dev/null
+++ b/src/common.h
@@ -0,0 +1,41 @@
+/*
+ * common.h - Shared utilities for ushow and uterm
+ */
+
+#ifndef COMMON_H
+#define COMMON_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * Apply thread settings for kdtree and OpenMP.
+ *   user_threads > 0: use that value for both kdtree and omp_set_num_threads.
+ *   user_threads <= 0: leave kdtree default; if OMP_NUM_THREADS is unset,
+ *                      set omp_set_num_threads to 4.
+ */
+void apply_thread_settings(int user_threads);
+
+/*
+ * Parse a CF-convention "units since origin" string.
+ * Returns 1 on success, 0 on failure.
+ *   unit_seconds: conversion factor (e.g. 86400 for days)
+ *   y,mo,d,h,mi,sec: parsed origin date/time components
+ */
+int parse_time_units(const char *units, double *unit_seconds,
+                     int *y, int *mo, int *d, int *h, int *mi, double *sec);
+
+/*
+ * Calendar arithmetic helpers (proleptic Gregorian).
+ */
+int64_t days_from_civil(int y, unsigned m, unsigned d);
+void civil_from_days(int64_t z, int *y, unsigned *m, unsigned *d);
+
+/*
+ * Format a CF time value as "YYYY-MM-DD HH:MM:SS" (or "YYYY-MM-DD" when
+ * the time-of-day is exactly midnight).
+ * Returns 1 on success, 0 on failure.
+ */
+int format_time_from_units(char *out, size_t outlen, double value, const char *units);
+
+#endif /* COMMON_H */
diff --git a/src/file_grib.h b/src/file_grib.h
index c733b90..b6cb08f 100644
--- a/src/file_grib.h
+++ b/src/file_grib.h
@@ -8,7 +8,7 @@
 #ifndef FILE_GRIB_H
 #define FILE_GRIB_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 #ifdef HAVE_GRIB
 
diff --git a/src/file_mitgcm.c b/src/file_mitgcm.c
index e4f8827..4076732 100644
--- a/src/file_mitgcm.c
+++ b/src/file_mitgcm.c
@@ -407,7 +407,7 @@ USFile *mitgcm_open(const char *path) {
     /* Allocate store */
     MitgcmStore *store = calloc(1, sizeof(MitgcmStore));
     if (!store) return NULL;
-    strncpy(store->directory, directory, MAX_NAME_LEN - 1);
+    snprintf(store->directory, sizeof(store->directory), "%s", directory);
     store->nx = nx;
     store->ny = ny;
     store->nz = nz;
@@ -473,7 +473,7 @@ USFile *mitgcm_open(const char *path) {
               free(store); return NULL; }
 
     f->file_type = FILE_TYPE_MITGCM;
-    strncpy(f->filename, directory, MAX_NAME_LEN - 1);
+    snprintf(f->filename, sizeof(f->filename), "%s", directory);
     f->mitgcm_data = store;
 
     return f;
@@ -487,7 +487,7 @@ USMesh *mitgcm_create_mesh(USFile *file) {
     size_t n_points = (size_t)ny * nx;
 
     /* Read XC.data and YC.data */
-    char xc_path[MAX_NAME_LEN], yc_path[MAX_NAME_LEN];
+    char xc_path[MAX_NAME_LEN + 16], yc_path[MAX_NAME_LEN + 16];
     snprintf(xc_path, sizeof(xc_path), "%s/XC.data", store->directory);
     snprintf(yc_path, sizeof(yc_path), "%s/YC.data", store->directory);
 
@@ -637,7 +637,8 @@ USVar *mitgcm_scan_variables(USFile *f, USMesh *m) {
             if (strcmp(prefixes[i], prefix) == 0) { found = 1; break; }
         }
         if (!found && n_prefixes < 64) {
-            strncpy(prefixes[n_prefixes++], prefix, MAX_NAME_LEN - 1);
+            snprintf(prefixes[n_prefixes], MAX_NAME_LEN, "%s", prefix);
+            n_prefixes++;
         }
     }
     closedir(dir);
@@ -659,7 +660,7 @@ USVar *mitgcm_scan_variables(USFile *f, USMesh *m) {
         if (!iterations || n_iters == 0) { free(iterations); continue; }
 
         /* Parse meta from first iteration to get field info */
-        char meta_path[MAX_NAME_LEN];
+        char meta_path[MAX_NAME_LEN * 2 + 32];
         snprintf(meta_path, sizeof(meta_path), "%s/%s.%010d.meta",
                  store->directory, prefixes[pi], iterations[0]);
 
@@ -683,9 +684,9 @@ USVar *mitgcm_scan_variables(USFile *f, USMesh *m) {
 
             /* Name */
             if (minfo.n_fields > 0 && minfo.fields[fi][0]) {
-                strncpy(var->name, minfo.fields[fi], MAX_NAME_LEN - 1);
+                snprintf(var->name, sizeof(var->name), "%s", minfo.fields[fi]);
             } else {
-                strncpy(var->name, prefixes[pi], MAX_NAME_LEN - 1);
+                snprintf(var->name, sizeof(var->name), "%s", prefixes[pi]);
             }
 
             var->mesh = m;
@@ -726,7 +727,7 @@ USVar *mitgcm_scan_variables(USFile *f, USMesh *m) {
             /* Private data */
             MitgcmVarData *vd = calloc(1, sizeof(MitgcmVarData));
             if (!vd) { free(var); continue; }
-            strncpy(vd->prefix, prefixes[pi], MAX_NAME_LEN - 1);
+            snprintf(vd->prefix, sizeof(vd->prefix), "%s", prefixes[pi]);
             vd->field_index = fi;
             vd->iterations = malloc(n_iters * sizeof(int));
             if (vd->iterations) {
@@ -801,7 +802,7 @@ int mitgcm_read_slice(USVar *var, size_t time_idx, size_t depth_idx, float *data
     if ((int)time_idx >= vd->n_iterations) return -1;
 
     /* Build data file path */
-    char data_path[MAX_NAME_LEN];
+    char data_path[MAX_NAME_LEN * 2 + 32];
     snprintf(data_path, sizeof(data_path), "%s/%s.%010d.data",
              store->directory, vd->prefix, vd->iterations[time_idx]);
 
@@ -1054,7 +1055,7 @@ int mitgcm_read_timeseries(USVar *var, size_t node_idx, size_t depth_idx,
         times[t] = (double)vd->iterations[t];
 
         /* Build path and read single value */
-        char data_path[MAX_NAME_LEN];
+        char data_path[MAX_NAME_LEN * 2 + 32];
         snprintf(data_path, sizeof(data_path), "%s/%s.%010d.data",
                  store->directory, vd->prefix, vd->iterations[t]);
 
diff --git a/src/file_mitgcm.h b/src/file_mitgcm.h
index 14d1bf7..01e8d97 100644
--- a/src/file_mitgcm.h
+++ b/src/file_mitgcm.h
@@ -8,7 +8,7 @@
 #ifndef FILE_MITGCM_H
 #define FILE_MITGCM_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Check if a path looks like MITgcm data (directory with .meta files,
diff --git a/src/file_netcdf.h b/src/file_netcdf.h
index c9fd082..dbbd03a 100644
--- a/src/file_netcdf.h
+++ b/src/file_netcdf.h
@@ -5,7 +5,7 @@
 #ifndef FILE_NETCDF_H
 #define FILE_NETCDF_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Open a NetCDF file and create file structure.
diff --git a/src/file_zarr.h b/src/file_zarr.h
index e5ad073..4f4d037 100644
--- a/src/file_zarr.h
+++ b/src/file_zarr.h
@@ -8,7 +8,7 @@
 #ifndef FILE_ZARR_H
 #define FILE_ZARR_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 #ifdef HAVE_ZARR
 
diff --git a/src/healpix.h b/src/healpix.h
index 74f382d..c3a80b8 100644
--- a/src/healpix.h
+++ b/src/healpix.h
@@ -9,7 +9,7 @@
 #ifndef HEALPIX_H
 #define HEALPIX_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Generate triangular element connectivity for a mesh whose points are
diff --git a/src/interface/timeseries_popup.h b/src/interface/timeseries_popup.h
index 9a65b66..2ea98d4 100644
--- a/src/interface/timeseries_popup.h
+++ b/src/interface/timeseries_popup.h
@@ -9,7 +9,7 @@
 #define TIMESERIES_POPUP_H
 
 #include <X11/Intrinsic.h>
-#include "../ushow.defines.h"
+#include "../us_types.h"
 
 /*
  * Initialize the timeseries popup widgets.
diff --git a/src/interface/x_interface.h b/src/interface/x_interface.h
index a0dd6ba..c96f107 100644
--- a/src/interface/x_interface.h
+++ b/src/interface/x_interface.h
@@ -5,7 +5,7 @@
 #ifndef X_INTERFACE_H
 #define X_INTERFACE_H
 
-#include "../ushow.defines.h"
+#include "../us_types.h"
 
 /*
  * Set light theme (call before x_init). Default is dark theme.
diff --git a/src/kdtree.c b/src/kdtree.c
index 488f6c0..27efda8 100644
--- a/src/kdtree.c
+++ b/src/kdtree.c
@@ -1,22 +1,61 @@
 /*
- * kdtree.c - Simple KDTree implementation for 3D nearest-neighbor queries
+ * kdtree.c - Advanced KDTree implementation for 3D nearest-neighbor queries
  *
- * Uses median-split construction and recursive nearest-neighbor search.
- * Optimized for the case of building once and querying many times.
+ * Inspired by the algorithms used in libkdtree by Jörg Dietrich
+ * (https://github.com/joergdietrich/libkdtree, LGPL-2.0).
+ * No code was copied; this is an independent reimplementation using
+ * standard kd-tree techniques (hyperrectangle-bounded nodes,
+ * parallel construction, multi-dimensional pruning) adapted for
+ * 3D double-precision coordinates with the existing public API.
  */
 
+#define _GNU_SOURCE  /* for qsort_r on Linux */
 #include "kdtree.h"
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
 #include <float.h>
+#include <unistd.h>
+#include <pthread.h>
 
 #define KDTREE_DIM 3
 
-/* KDTree node */
+/* Minimum number of points before spawning a new thread */
+#define KDTREE_THREAD_THRESHOLD 4096
+
+/* Default thread count when neither set by user nor OMP_NUM_THREADS */
+#define KDTREE_DEFAULT_THREADS 4
+
+/* Module-level thread limit: -1 means "not explicitly set" */
+static int g_max_threads = -1;
+
+void kdtree_set_max_threads(int n) {
+    if (n > 0) g_max_threads = n;
+}
+
+/* Resolve effective thread count:
+ *   1. Explicit call to kdtree_set_max_threads()
+ *   2. OMP_NUM_THREADS environment variable
+ *   3. Number of online CPUs (sysconf)
+ *   4. KDTREE_DEFAULT_THREADS
+ */
+static int get_max_threads(void) {
+    if (g_max_threads > 0) return g_max_threads;
+    const char *env = getenv("OMP_NUM_THREADS");
+    if (env) {
+        int n = atoi(env);
+        if (n > 0) return n;
+    }
+    return KDTREE_DEFAULT_THREADS;
+}
+
+/* KDTree node with hyperrectangle bounds (from libkdtree design) */
 typedef struct KDNode {
-    size_t          idx;        /* Original point index */
-    double          point[KDTREE_DIM];
+    size_t          idx;                  /* Original point index */
+    double          location[KDTREE_DIM]; /* Node position */
+    double          hr_min[KDTREE_DIM];   /* Hyperrectangle min bounds */
+    double          hr_max[KDTREE_DIM];   /* Hyperrectangle max bounds */
+    int             split;                /* Split axis */
     struct KDNode  *left;
     struct KDNode  *right;
 } KDNode;
@@ -28,56 +67,166 @@ struct KDTree {
     double     *points;         /* Copy of original points */
 };
 
-/* Comparison context for qsort */
+/* Thread argument for parallel tree construction (from libkdtree design) */
+typedef struct {
+    const double   *points;
+    size_t         *indices;
+    size_t          n;
+    double          hr_min[KDTREE_DIM];
+    double          hr_max[KDTREE_DIM];
+    int             depth;
+    int             max_threads;
+} KDBuildArg;
+
+/* -------------------------------------------------------------------
+ * Comparison for qsort_r (thread-safe, no global state)
+ * ------------------------------------------------------------------- */
+
 typedef struct {
     const double *points;
     int axis;
-} SortContext;
+} SortCtx;
 
-static SortContext sort_ctx;
-
-/* Comparison function for sorting indices by coordinate */
-static int compare_by_axis(const void *a, const void *b) {
+static int compare_by_axis_r(const void *a, const void *b, void *arg) {
+    SortCtx *ctx = (SortCtx *)arg;
     size_t ia = *(const size_t *)a;
     size_t ib = *(const size_t *)b;
-    double va = sort_ctx.points[ia * KDTREE_DIM + sort_ctx.axis];
-    double vb = sort_ctx.points[ib * KDTREE_DIM + sort_ctx.axis];
+    double va = ctx->points[ia * KDTREE_DIM + ctx->axis];
+    double vb = ctx->points[ib * KDTREE_DIM + ctx->axis];
     if (va < vb) return -1;
-    if (va > vb) return 1;
+    if (va > vb) return  1;
     return 0;
 }
 
-/* Build KDTree recursively */
-static KDNode *build_tree(const double *points, size_t *indices,
-                          size_t n, int depth) {
+/* -------------------------------------------------------------------
+ * Squared Euclidean distance
+ * ------------------------------------------------------------------- */
+
+static inline double dist_sq(const double *a, const double *b) {
+    double dx = a[0] - b[0];
+    double dy = a[1] - b[1];
+    double dz = a[2] - b[2];
+    return dx*dx + dy*dy + dz*dz;
+}
+
+/* -------------------------------------------------------------------
+ * Minimum squared distance from a point to a hyperrectangle.
+ * This is the key pruning improvement: instead of checking only the
+ * split-axis distance (simple impl) or the distance to the further
+ * node's split-axis bounds (original libkdtree), we compute the true
+ * minimum distance across all dimensions.
+ * ------------------------------------------------------------------- */
+
+static inline double min_dist_sq_to_hr(const double *query,
+                                       const double *hr_min,
+                                       const double *hr_max) {
+    double dsq = 0.0;
+    for (int d = 0; d < KDTREE_DIM; d++) {
+        if (query[d] < hr_min[d]) {
+            double diff = hr_min[d] - query[d];
+            dsq += diff * diff;
+        } else if (query[d] > hr_max[d]) {
+            double diff = query[d] - hr_max[d];
+            dsq += diff * diff;
+        }
+    }
+    return dsq;
+}
+
+/* -------------------------------------------------------------------
+ * Tree construction (adapted from libkdtree: kd_doBuildTree)
+ *
+ * Each node stores the bounding hyperrectangle for its subtree,
+ * enabling tighter pruning during nearest-neighbor search.
+ * Construction can be parallelized across POSIX threads.
+ * ------------------------------------------------------------------- */
+
+static KDNode *build_tree(const double *points, size_t *indices, size_t n,
+                          const double *hr_min, const double *hr_max,
+                          int depth, int max_threads);
+static void *build_tree_thread(void *arg);
+
+static KDNode *build_tree(const double *points, size_t *indices, size_t n,
+                          const double *hr_min, const double *hr_max,
+                          int depth, int max_threads) {
     if (n == 0) return NULL;
 
     int axis = depth % KDTREE_DIM;
 
-    /* Sort indices by current axis */
-    sort_ctx.points = points;
-    sort_ctx.axis = axis;
-    qsort(indices, n, sizeof(size_t), compare_by_axis);
+    /* Thread-safe sort by current axis (cf. libkdtree pmergesort) */
+    SortCtx ctx = { .points = points, .axis = axis };
+    qsort_r(indices, n, sizeof(size_t), compare_by_axis_r, &ctx);
 
-    /* Find median */
     size_t median = n / 2;
 
-    /* Create node */
+    /* Allocate node with hyperrectangle bounds (cf. libkdtree kd_allocNode) */
     KDNode *node = malloc(sizeof(KDNode));
     if (!node) return NULL;
 
-    node->idx = indices[median];
-    node->point[0] = points[node->idx * KDTREE_DIM + 0];
-    node->point[1] = points[node->idx * KDTREE_DIM + 1];
-    node->point[2] = points[node->idx * KDTREE_DIM + 2];
-
-    /* Build subtrees */
-    node->left = build_tree(points, indices, median, depth + 1);
-    node->right = build_tree(points, indices + median + 1, n - median - 1, depth + 1);
+    node->idx   = indices[median];
+    node->split = axis;
+    memcpy(node->location, &points[node->idx * KDTREE_DIM],
+           KDTREE_DIM * sizeof(double));
+    memcpy(node->hr_min, hr_min, KDTREE_DIM * sizeof(double));
+    memcpy(node->hr_max, hr_max, KDTREE_DIM * sizeof(double));
+    node->left  = NULL;
+    node->right = NULL;
+
+    if (n == 1) return node;
+
+    /* Child hyperrectangle bounds split at the median's coordinate
+     * (cf. libkdtree: tmpMaxLeft[sortaxis] = node->location[sortaxis]) */
+    double left_max[KDTREE_DIM], right_min[KDTREE_DIM];
+    memcpy(left_max,  hr_max,  KDTREE_DIM * sizeof(double));
+    memcpy(right_min, hr_min,  KDTREE_DIM * sizeof(double));
+    left_max[axis]  = node->location[axis];
+    right_min[axis] = node->location[axis];
+
+    /* Parallel construction (cf. libkdtree: pthread_create in kd_doBuildTree) */
+    if (max_threads > 1 && n > KDTREE_THREAD_THRESHOLD) {
+        KDBuildArg left_arg = {
+            .points      = points,
+            .indices     = indices,
+            .n           = median,
+            .depth       = depth + 1,
+            .max_threads = max_threads / 2
+        };
+        memcpy(left_arg.hr_min, hr_min,   KDTREE_DIM * sizeof(double));
+        memcpy(left_arg.hr_max, left_max, KDTREE_DIM * sizeof(double));
+
+        pthread_t tid;
+        if (pthread_create(&tid, NULL, build_tree_thread, &left_arg) == 0) {
+            /* Build right subtree in this thread */
+            node->right = build_tree(points, indices + median + 1,
+                                     n - median - 1, right_min, hr_max,
+                                     depth + 1, max_threads / 2);
+            pthread_join(tid, (void **)&node->left);
+        } else {
+            /* pthread_create failed – fall back to sequential */
+            goto sequential;
+        }
+    } else {
+sequential:
+        node->left  = build_tree(points, indices, median,
+                                 hr_min, left_max, depth + 1, max_threads);
+        node->right = build_tree(points, indices + median + 1,
+                                 n - median - 1, right_min, hr_max,
+                                 depth + 1, max_threads);
+    }
 
     return node;
 }
 
+static void *build_tree_thread(void *arg) {
+    KDBuildArg *d = (KDBuildArg *)arg;
+    return build_tree(d->points, d->indices, d->n,
+                      d->hr_min, d->hr_max, d->depth, d->max_threads);
+}
+
+/* -------------------------------------------------------------------
+ * Public: create tree
+ * ------------------------------------------------------------------- */
+
 KDTree *kdtree_create(const double *points, size_t n_points) {
     if (!points || n_points == 0) return NULL;
 
@@ -101,12 +250,26 @@ KDTree *kdtree_create(const double *points, size_t n_points) {
         free(tree);
         return NULL;
     }
+
+    /* Compute bounding hyperrectangle (cf. libkdtree: min/max args) */
+    double bb_min[KDTREE_DIM], bb_max[KDTREE_DIM];
+    for (int d = 0; d < KDTREE_DIM; d++) {
+        bb_min[d] =  DBL_MAX;
+        bb_max[d] = -DBL_MAX;
+    }
     for (size_t i = 0; i < n_points; i++) {
         indices[i] = i;
+        for (int d = 0; d < KDTREE_DIM; d++) {
+            double v = points[i * KDTREE_DIM + d];
+            if (v < bb_min[d]) bb_min[d] = v;
+            if (v > bb_max[d]) bb_max[d] = v;
+        }
     }
 
-    /* Build tree */
-    tree->root = build_tree(tree->points, indices, n_points, 0);
+    /* Resolve thread count: CLI > OMP_NUM_THREADS > default */
+    int max_threads = get_max_threads();
+    tree->root = build_tree(tree->points, indices, n_points,
+                            bb_min, bb_max, 0, max_threads);
 
     free(indices);
 
@@ -119,39 +282,45 @@ KDTree *kdtree_create(const double *points, size_t n_points) {
     return tree;
 }
 
-/* Squared Euclidean distance */
-static inline double dist_sq(const double *a, const double *b) {
-    double dx = a[0] - b[0];
-    double dy = a[1] - b[1];
-    double dz = a[2] - b[2];
-    return dx*dx + dy*dy + dz*dz;
-}
+/* -------------------------------------------------------------------
+ * Nearest-neighbor search (adapted from libkdtree: kd_nearest)
+ *
+ * Uses hyperrectangle bounds to prune the further subtree: if the
+ * minimum distance from the query to the further child's bounding
+ * box exceeds the current best, the entire subtree is skipped.
+ * ------------------------------------------------------------------- */
 
-/* Recursive nearest neighbor search */
 static void search_nearest(const KDNode *node, const double *query,
-                           int depth, size_t *best_idx, double *best_dist_sq) {
+                           size_t *best_idx, double *best_dist_sq) {
     if (!node) return;
 
     /* Check current node */
-    double d = dist_sq(node->point, query);
+    double d = dist_sq(node->location, query);
     if (d < *best_dist_sq) {
         *best_dist_sq = d;
         *best_idx = node->idx;
     }
 
-    /* Determine which subtree to search first */
-    int axis = depth % KDTREE_DIM;
-    double diff = query[axis] - node->point[axis];
-
-    KDNode *first = (diff < 0) ? node->left : node->right;
-    KDNode *second = (diff < 0) ? node->right : node->left;
+    /* Determine nearer / further subtree (cf. libkdtree kd_nearest) */
+    const KDNode *nearer, *further;
+    if (query[node->split] < node->location[node->split]) {
+        nearer  = node->left;
+        further = node->right;
+    } else {
+        nearer  = node->right;
+        further = node->left;
+    }
 
     /* Search closer subtree first */
-    search_nearest(first, query, depth + 1, best_idx, best_dist_sq);
-
-    /* Check if we need to search the other subtree */
-    if (diff * diff < *best_dist_sq) {
-        search_nearest(second, query, depth + 1, best_idx, best_dist_sq);
+    search_nearest(nearer, query, best_idx, best_dist_sq);
+
+    /* Prune using minimum distance to further child's hyperrectangle.
+     * This is tighter than the single-axis check in the simple
+     * implementation, and uses all dimensions unlike the original
+     * libkdtree which only checked the split axis. */
+    if (further && min_dist_sq_to_hr(query, further->hr_min,
+                                     further->hr_max) < *best_dist_sq) {
+        search_nearest(further, query, best_idx, best_dist_sq);
     }
 }
 
@@ -163,16 +332,19 @@ void kdtree_query_nearest(const KDTree *tree, const double *query,
         return;
     }
 
-    *nn_dist = DBL_MAX;
+    double best_dist_sq = DBL_MAX;
     *nn_idx = 0;
 
-    search_nearest(tree->root, query, 0, nn_idx, nn_dist);
+    search_nearest(tree->root, query, nn_idx, &best_dist_sq);
 
     /* Return actual distance (not squared) */
-    *nn_dist = sqrt(*nn_dist);
+    *nn_dist = sqrt(best_dist_sq);
 }
 
-/* Free tree recursively */
+/* -------------------------------------------------------------------
+ * Cleanup (cf. libkdtree: kd_destroyTree / kd_freeNode)
+ * ------------------------------------------------------------------- */
+
 static void free_node(KDNode *node) {
     if (!node) return;
     free_node(node->left);
diff --git a/src/kdtree.h b/src/kdtree.h
index f91ea66..8ed6985 100644
--- a/src/kdtree.h
+++ b/src/kdtree.h
@@ -39,4 +39,12 @@ void kdtree_free(KDTree *tree);
  */
 size_t kdtree_size(const KDTree *tree);
 
+/*
+ * Set the maximum number of threads for parallel tree construction.
+ * If never called, kdtree_create uses OMP_NUM_THREADS (if set),
+ * otherwise falls back to KDTREE_DEFAULT_THREADS (4).
+ * A value <= 0 is ignored.
+ */
+void kdtree_set_max_threads(int n);
+
 #endif /* KDTREE_H */
diff --git a/src/mesh.h b/src/mesh.h
index 536c35c..7280128 100644
--- a/src/mesh.h
+++ b/src/mesh.h
@@ -5,7 +5,7 @@
 #ifndef MESH_H
 #define MESH_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Convert longitude/latitude to Cartesian on unit sphere.
diff --git a/src/projection.h b/src/projection.h
index 5c5cc71..fecf71f 100644
--- a/src/projection.h
+++ b/src/projection.h
@@ -5,7 +5,7 @@
 #ifndef PROJECTION_H
 #define PROJECTION_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Initialize target config with global equirectangular defaults.
diff --git a/src/regrid.h b/src/regrid.h
index f511f9d..d5093a3 100644
--- a/src/regrid.h
+++ b/src/regrid.h
@@ -5,7 +5,7 @@
 #ifndef REGRID_H
 #define REGRID_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 #include "mesh.h"
 
 /*
diff --git a/src/regrid_yac.h b/src/regrid_yac.h
index 5800ed3..09ae364 100644
--- a/src/regrid_yac.h
+++ b/src/regrid_yac.h
@@ -11,7 +11,7 @@
 
 #ifdef HAVE_YAC
 
-#include "ushow.defines.h"
+#include "us_types.h"
 #include "mesh.h"
 
 typedef enum {
diff --git a/src/ushow.defines.h b/src/us_types.h
similarity index 92%
rename from src/ushow.defines.h
rename to src/us_types.h
index ed8afe5..596d6a5 100644
--- a/src/ushow.defines.h
+++ b/src/us_types.h
@@ -1,11 +1,11 @@
 /*
- * ushow.defines.h - Data structures and constants for ushow
+ * us_types.h - Shared data structures and constants for ushow/uterm
  *
  * Unstructured data visualization tool
  */
 
-#ifndef USHOW_DEFINES_H
-#define USHOW_DEFINES_H
+#ifndef US_TYPES_H
+#define US_TYPES_H
 
 #include <stddef.h>
 
@@ -269,21 +269,6 @@ struct USView {
     int         frame_delay_ms;
 };
 
-/* Global options */
-typedef struct {
-    int         debug;
-    double      influence_radius;   /* Regrid influence radius in meters */
-    double      target_resolution;  /* Target grid resolution in degrees */
-    char        mesh_file[MAX_NAME_LEN];  /* Separate mesh file path */
-    int         frame_delay_ms;     /* Animation speed */
-    int         polygon_only;       /* Skip regridding, polygon mode only */
-    USTargetConfig target_config;   /* Target grid configuration */
-#ifdef HAVE_YAC
-    int         yac_method;        /* YAC interpolation method (-1 = disabled) */
-    int         yac_3d;            /* Fractional fill-value masking */
-#endif
-} USOptions;
-
 /* Dimension info for display */
 typedef struct {
     char        name[MAX_NAME_LEN];     /* Dimension name (e.g., "time", "depth") */
@@ -320,4 +305,4 @@ typedef struct {
     USColor    *colors;
 } USColormap;
 
-#endif /* USHOW_DEFINES_H */
+#endif /* US_TYPES_H */
diff --git a/src/ushow.c b/src/ushow.c
index f301ec8..2508f4e 100644
--- a/src/ushow.c
+++ b/src/ushow.c
@@ -4,7 +4,7 @@
  * Unstructured data visualization tool
  */
 
-#include "ushow.defines.h"
+#include "us_types.h"
 #include "mesh.h"
 #include "regrid.h"
 #ifdef HAVE_YAC
@@ -19,6 +19,7 @@
 #include "file_grib.h"
 #endif
 #include "kdtree.h"
+#include "common.h"
 #include "colormaps.h"
 #include "view.h"
 #include "interface/x_interface.h"
@@ -50,6 +51,21 @@ static USDimInfo *current_dim_info = NULL;
 static int n_current_dims = 0;
 
 /* Options */
+typedef struct {
+    int         debug;
+    double      influence_radius;   /* Regrid influence radius in meters */
+    double      target_resolution;  /* Target grid resolution in degrees */
+    char        mesh_file[MAX_NAME_LEN];  /* Separate mesh file path */
+    int         frame_delay_ms;     /* Animation speed */
+    int         polygon_only;       /* Skip regridding, polygon mode only */
+    USTargetConfig target_config;   /* Target grid configuration */
+    int         user_threads;      /* CLI --threads value (0 = not set) */
+#ifdef HAVE_YAC
+    int         yac_method;        /* YAC interpolation method (-1 = disabled) */
+    int         yac_3d;            /* Fractional fill-value masking */
+#endif
+} USOptions;
+
 static USOptions options = {
     .debug = 0,
     .influence_radius = DEFAULT_INFLUENCE_RADIUS_M,
@@ -59,6 +75,7 @@ static USOptions options = {
                        .lon_min = -180, .lon_max = 180,
                        .lat_min = -90, .lat_max = 90,
                        .cutoff_lat = 60.0 },
+    .user_threads = 0,
 #ifdef HAVE_YAC
     .yac_method = -1,
     .yac_3d = 0,
@@ -70,7 +87,6 @@ static void update_display(void);
 static void animation_tick(void);
 static void update_dim_info_current(void);
 static void update_dim_label(void);
-static int format_time_from_units(char *out, size_t outlen, double value, const char *units);
 static void on_mouse_click(int px, int py);
 
 /* Callbacks */
@@ -402,10 +418,10 @@ static void on_mouse_click(int px, int py) {
 
     /* Build title */
     if (current_var->units[0]) {
-        snprintf(ts_data.title, sizeof(ts_data.title), "%s (%s) at %.2f, %.2f",
+        snprintf(ts_data.title, sizeof(ts_data.title), "%.200s (%.200s) at %.2f, %.2f",
                  current_var->name, current_var->units, lon, lat);
     } else {
-        snprintf(ts_data.title, sizeof(ts_data.title), "%s at %.2f, %.2f",
+        snprintf(ts_data.title, sizeof(ts_data.title), "%.200s at %.2f, %.2f",
                  current_var->name, lon, lat);
     }
 
@@ -418,7 +434,7 @@ static void on_mouse_click(int px, int py) {
         for (int i = 0; i < n_current_dims; i++) {
             if (strcmp(current_dim_info[i].name, time_dim_name) == 0) {
                 if (current_dim_info[i].units[0]) {
-                    strncpy(ts_data.x_label, current_dim_info[i].units, sizeof(ts_data.x_label) - 1);
+                    snprintf(ts_data.x_label, sizeof(ts_data.x_label), "%s", current_dim_info[i].units);
                 }
                 break;
             }
@@ -429,10 +445,10 @@ static void on_mouse_click(int px, int py) {
     }
 
     if (current_var->units[0]) {
-        snprintf(ts_data.y_label, sizeof(ts_data.y_label), "%s (%s)",
+        snprintf(ts_data.y_label, sizeof(ts_data.y_label), "%.120s (%.120s)",
                  current_var->name, current_var->units);
     } else {
-        strncpy(ts_data.y_label, current_var->name, sizeof(ts_data.y_label) - 1);
+        snprintf(ts_data.y_label, sizeof(ts_data.y_label), "%s", current_var->name);
     }
 
     printf("Time series: %zu points (%zu valid)\n", n_out, ts_data.n_valid);
@@ -523,13 +539,13 @@ static void on_range_button(void) {
 
 static void on_render_mode_toggle(void) {
     if (!view) return;
-    
+
     /* In polygon-only mode, don't allow switching */
     if (options.polygon_only) {
         printf("Polygon-only mode: cannot switch to interpolate mode\n");
         return;
     }
-    
+
     int result = view_toggle_render_mode(view);
     if (result >= 0) {
         const char *mode_name = (result == RENDER_MODE_POLYGON) ? "Polygon" : "Interp";
@@ -615,105 +631,6 @@ static void update_dim_info_current(void) {
     }
 }
 
-static int parse_time_units(const char *units, double *unit_seconds,
-                            int *y, int *mo, int *d, int *h, int *mi, double *sec) {
-    if (!units || !unit_seconds || !y || !mo || !d || !h || !mi || !sec) return 0;
-
-    const char *since = strstr(units, "since");
-    if (!since) return 0;
-
-    char unit_buf[32] = {0};
-    if (sscanf(units, "%31s", unit_buf) != 1) return 0;
-
-    /* Normalize unit token to lower case */
-    for (char *p = unit_buf; *p; ++p) {
-        if (*p >= 'A' && *p <= 'Z') *p = (char)(*p - 'A' + 'a');
-    }
-
-    if (strcmp(unit_buf, "seconds") == 0 || strcmp(unit_buf, "second") == 0 ||
-        strcmp(unit_buf, "secs") == 0 || strcmp(unit_buf, "sec") == 0 || strcmp(unit_buf, "s") == 0) {
-        *unit_seconds = 1.0;
-    } else if (strcmp(unit_buf, "minutes") == 0 || strcmp(unit_buf, "minute") == 0 ||
-               strcmp(unit_buf, "mins") == 0 || strcmp(unit_buf, "min") == 0) {
-        *unit_seconds = 60.0;
-    } else if (strcmp(unit_buf, "hours") == 0 || strcmp(unit_buf, "hour") == 0 ||
-               strcmp(unit_buf, "hrs") == 0 || strcmp(unit_buf, "hr") == 0) {
-        *unit_seconds = 3600.0;
-    } else if (strcmp(unit_buf, "days") == 0 || strcmp(unit_buf, "day") == 0) {
-        *unit_seconds = 86400.0;
-    } else {
-        return 0;
-    }
-
-    /* Parse origin date/time after "since" */
-    const char *p = since + 5;
-    while (*p == ' ') p++;
-    int n = sscanf(p, "%d-%d-%d %d:%d:%lf", y, mo, d, h, mi, sec);
-    if (n < 3) return 0;
-    if (n == 3) { *h = 0; *mi = 0; *sec = 0.0; }
-    return 1;
-}
-
-static int64_t days_from_civil(int y, unsigned m, unsigned d) {
-    y -= m <= 2;
-    const int era = (y >= 0 ? y : y - 399) / 400;
-    const unsigned yoe = (unsigned)(y - era * 400);
-    const unsigned doy = (153 * (m + (m > 2 ? -3 : 9)) + 2) / 5 + d - 1;
-    const unsigned doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;
-    return (int64_t)(era * 146097 + (int)doe - 719468);
-}
-
-static void civil_from_days(int64_t z, int *y, unsigned *m, unsigned *d) {
-    z += 719468;
-    const int era = (z >= 0 ? z : z - 146096) / 146097;
-    const unsigned doe = (unsigned)(z - era * 146097);
-    const unsigned yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
-    int y_tmp = (int)(yoe) + era * 400;
-    const unsigned doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
-    const unsigned mp = (5 * doy + 2) / 153;
-    const unsigned d_tmp = doy - (153 * mp + 2) / 5 + 1;
-    const unsigned m_tmp = mp + (mp < 10 ? 3 : -9);
-    y_tmp += (m_tmp <= 2);
-
-    *y = y_tmp;
-    *m = m_tmp;
-    *d = d_tmp;
-}
-
-static int format_time_from_units(char *out, size_t outlen, double value, const char *units) {
-    double unit_seconds = 0.0;
-    int y, mo, d, h, mi;
-    double sec;
-    if (!parse_time_units(units, &unit_seconds, &y, &mo, &d, &h, &mi, &sec)) {
-        return 0;
-    }
-
-    int64_t days = days_from_civil(y, (unsigned)mo, (unsigned)d);
-    double total_sec = (double)days * 86400.0 + (double)h * 3600.0 + (double)mi * 60.0 + sec;
-    total_sec += value * unit_seconds;
-
-    int64_t out_days = (int64_t)(total_sec / 86400.0);
-    double rem = total_sec - (double)out_days * 86400.0;
-    if (rem < 0) {
-        rem += 86400.0;
-        out_days -= 1;
-    }
-
-    int out_y;
-    unsigned out_m, out_d;
-    civil_from_days(out_days, &out_y, &out_m, &out_d);
-
-    int out_h = (int)(rem / 3600.0);
-    rem -= out_h * 3600.0;
-    int out_mi = (int)(rem / 60.0);
-    rem -= out_mi * 60.0;
-    int out_s = (int)(rem + 0.5);
-
-    snprintf(out, outlen, "%04d-%02u-%02u %02d:%02d:%02d",
-             out_y, out_m, out_d, out_h, out_mi, out_s);
-    return 1;
-}
-
 static const USDimInfo *find_dim_info_for_dim(const char *dim_name) {
     if (!current_dim_info || !dim_name) return NULL;
     for (int i = 0; i < n_current_dims; i++) {
@@ -874,6 +791,8 @@ static void print_usage(const char *prog) {
     fprintf(stderr, "      --yac-3d           Fractional fill-value masking for 3D variables\n");
 #endif
     fprintf(stderr, "      --light            Use light theme (default: dark)\n");
+    fprintf(stderr, "  -t, --threads <n>      Max threads\n");
+    fprintf(stderr, "                         (default: OMP_NUM_THREADS or 4)\n");
     fprintf(stderr, "  -h, --help             Show this help\n");
     fprintf(stderr, "\nExamples:\n");
     fprintf(stderr, "  %s data.nc                           # Single file\n", prog);
@@ -882,37 +801,49 @@ static void print_usage(const char *prog) {
     fprintf(stderr, "  %s data.1960.nc data.1961.nc -m mesh # Multi-file explicit\n", prog);
 }
 
-int main(int argc, char *argv[]) {
-    const char *mesh_filename = NULL;
-    int n_data_files = 0;
-    const char **data_filenames = NULL;
+/*
+ * Parse command-line options into the global `options` struct.
+ * Returns 0 on success, >0 for clean exit (--help), <0 on error.
+ * Sets *first_data_arg to the index of the first non-option argument.
+ */
+static int parse_options(int argc, char **argv, int *first_data_arg) {
+    /* Long-only option codes (above ASCII range to avoid conflicts) */
+    enum {
+        OPT_BOX = 256,
+        OPT_POLAR,
+        OPT_CUTOFF,
+        OPT_YAC,
+        OPT_YAC_METHOD,
+        OPT_YAC_3D,
+        OPT_LIGHT,
+    };
 
-    /* Parse command line options */
     static struct option long_options[] = {
         {"mesh",         required_argument, 0, 'm'},
         {"resolution",   required_argument, 0, 'r'},
         {"influence",    required_argument, 0, 'i'},
         {"delay",        required_argument, 0, 'd'},
         {"polygon-only", no_argument,       0, 'p'},
-        {"box",          required_argument, 0, 1200},
-        {"polar",        required_argument, 0, 1201},
-        {"cutoff",       required_argument, 0, 1202},
+        {"box",          required_argument, 0, OPT_BOX},
+        {"polar",        required_argument, 0, OPT_POLAR},
+        {"cutoff",       required_argument, 0, OPT_CUTOFF},
 #ifdef HAVE_YAC
-        {"yac",          no_argument,       0, 1099},
-        {"yac-method",   required_argument, 0, 1100},
-        {"yac-3d",       no_argument,       0, 1101},
+        {"yac",          no_argument,       0, OPT_YAC},
+        {"yac-method",   required_argument, 0, OPT_YAC_METHOD},
+        {"yac-3d",       no_argument,       0, OPT_YAC_3D},
 #endif
-        {"light",        no_argument,       0, 1300},
+        {"light",        no_argument,       0, OPT_LIGHT},
+        {"threads",      required_argument, 0, 't'},
         {"help",         no_argument,       0, 'h'},
         {0, 0, 0, 0}
     };
 
     int opt;
-    while ((opt = getopt_long(argc, argv, "m:r:i:d:ph", long_options, NULL)) != -1) {
+    while ((opt = getopt_long(argc, argv, "m:r:i:d:pt:h", long_options, NULL)) != -1) {
         switch (opt) {
             case 'm':
-                mesh_filename = optarg;
                 strncpy(options.mesh_file, optarg, MAX_NAME_LEN - 1);
+                options.mesh_file[MAX_NAME_LEN - 1] = '\0';
                 break;
             case 'r':
                 options.target_resolution = atof(optarg);
@@ -927,31 +858,31 @@ int main(int argc, char *argv[]) {
                 options.polygon_only = 1;
                 break;
 #ifdef HAVE_YAC
-            case 1099:
+            case OPT_YAC:
                 options.yac_method = (int)YAC_METHOD_AVERAGE_ARITH;
                 break;
-            case 1100: {
+            case OPT_YAC_METHOD: {
                 USYacMethod ym;
                 if (yac_method_parse(optarg, &ym) != 0) {
                     fprintf(stderr, "Unknown YAC method: %s\n", optarg);
                     fprintf(stderr, "Available: nnn1, nnn4dist, nnn4gauss, "
                             "avg_arith, avg_dist, avg_bary, conserv1, conserv2\n");
-                    return 1;
+                    return -1;
                 }
                 options.yac_method = (int)ym;
                 break;
             }
-            case 1101:
+            case OPT_YAC_3D:
                 options.yac_3d = 1;
                 if (options.yac_method < 0)
                     options.yac_method = (int)YAC_METHOD_AVERAGE_ARITH;
                 break;
 #endif
-            case 1200: {
+            case OPT_BOX: {
                 double w, e, s, n;
                 if (sscanf(optarg, "%lf,%lf,%lf,%lf", &w, &e, &s, &n) != 4) {
                     fprintf(stderr, "Invalid --box format, use W,E,S,N (e.g. -10,30,35,70)\n");
-                    return 1;
+                    return -1;
                 }
                 options.target_config.lon_min = w;
                 options.target_config.lon_max = e;
@@ -959,38 +890,63 @@ int main(int argc, char *argv[]) {
                 options.target_config.lat_max = n;
                 break;
             }
-            case 1201:
+            case OPT_POLAR:
                 if (strcmp(optarg, "north") == 0) {
                     options.target_config.projection = PROJ_LAEA_NORTH;
                 } else if (strcmp(optarg, "south") == 0) {
                     options.target_config.projection = PROJ_LAEA_SOUTH;
                 } else {
                     fprintf(stderr, "Invalid --polar value: %s (use north or south)\n", optarg);
-                    return 1;
+                    return -1;
                 }
                 break;
-            case 1202:
+            case OPT_CUTOFF:
                 options.target_config.cutoff_lat = atof(optarg);
                 break;
-            case 1300:
+            case OPT_LIGHT:
                 x_set_light_theme();
                 break;
+            case 't': {
+                int nt = atoi(optarg);
+                if (nt < 1) {
+                    fprintf(stderr, "Invalid --threads value: %s (must be >= 1)\n", optarg);
+                    return -1;
+                }
+                options.user_threads = nt;
+                break;
+            }
             case 'h':
+                print_usage(argv[0]);
+                return 1;
             default:
                 print_usage(argv[0]);
-                return (opt == 'h') ? 0 : 1;
+                return -1;
         }
     }
 
     if (optind >= argc) {
         fprintf(stderr, "Error: No data file specified\n");
         print_usage(argv[0]);
-        return 1;
+        return -1;
+    }
+
+    *first_data_arg = optind;
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+    int first_data_arg = 0;
+    int parse_rc = parse_options(argc, argv, &first_data_arg);
+    if (parse_rc != 0) {
+        return (parse_rc > 0) ? 0 : 1;
     }
 
-    /* Collect data file arguments */
-    n_data_files = argc - optind;
-    data_filenames = (const char **)&argv[optind];
+    int n_data_files = argc - first_data_arg;
+    const char **data_filenames = (const char **)&argv[first_data_arg];
+    const char *mesh_filename = options.mesh_file[0] ? options.mesh_file : NULL;
+
+    /* Apply thread settings: CLI > OMP_NUM_THREADS > default 4 */
+    apply_thread_settings(options.user_threads);
 
     printf("=== ushow: Unstructured Data Viewer ===\n\n");
 
diff --git a/src/uterm.c b/src/uterm.c
index 702f040..776f04d 100644
--- a/src/uterm.c
+++ b/src/uterm.c
@@ -5,9 +5,11 @@
  * (netCDF/Zarr -> mesh -> regrid -> view) and renders frames as text.
  */
 
-#include "ushow.defines.h"
+#include "us_types.h"
 #include "mesh.h"
 #include "regrid.h"
+#include "kdtree.h"
+#include "common.h"
 #ifdef HAVE_YAC
 #include "regrid_yac.h"
 #endif
@@ -45,8 +47,6 @@
 #define CP_LOWER_HALF_BLOCK 0x2584
 #define CP_FULL_BLOCK 0x2588
 
-static int format_time_from_units(char *out, size_t outlen, double value, const char *units);
-
 /* Global state */
 static USFile *file = NULL;
 static USFileSet *fileset = NULL;
@@ -77,6 +77,7 @@ typedef struct {
     char mesh_file[MAX_NAME_LEN];
     char glyph_ramp[128];
     USTargetConfig target_config;
+    int user_threads;        /* CLI --threads value (0 = not set) */
 #ifdef HAVE_YAC
     int yac_method;
     int yac_3d;
@@ -95,6 +96,7 @@ static UTermOptions options = {
                        .lon_min = -180, .lon_max = 180,
                        .lat_min = -90, .lat_max = 90,
                        .cutoff_lat = 60.0 },
+    .user_threads = 0,
 #ifdef HAVE_YAC
     .yac_method = -1,
     .yac_3d = 0,
@@ -256,6 +258,8 @@ static void print_usage(const char *prog) {
     fprintf(stderr, "                         conserv1, conserv2\n");
     fprintf(stderr, "      --yac-3d           Fractional fill-value masking for 3D variables\n");
 #endif
+    fprintf(stderr, "  -t, --threads <n>      Max threads\n");
+    fprintf(stderr, "                         (default: OMP_NUM_THREADS or 4)\n");
     fprintf(stderr, "  -h, --help             Show this help\n\n");
 
     fprintf(stderr, "Keys:\n");
@@ -394,84 +398,6 @@ static void save_frame(void) {
     }
 }
 
-static int parse_time_units(const char *units, double *unit_seconds,
-                            int *origin_year, int *origin_month, int *origin_day,
-                            int *origin_hour, int *origin_minute, int *origin_second) {
-    if (!units || !unit_seconds || !origin_year || !origin_month || !origin_day ||
-        !origin_hour || !origin_minute || !origin_second) {
-        return 0;
-    }
-
-    const char *since = strstr(units, " since ");
-    if (!since) return 0;
-
-    if (strncmp(units, "days", since - units) == 0) {
-        *unit_seconds = 86400.0;
-    } else if (strncmp(units, "day", since - units) == 0) {
-        *unit_seconds = 86400.0;
-    } else if (strncmp(units, "hours", since - units) == 0) {
-        *unit_seconds = 3600.0;
-    } else if (strncmp(units, "hour", since - units) == 0) {
-        *unit_seconds = 3600.0;
-    } else if (strncmp(units, "minutes", since - units) == 0) {
-        *unit_seconds = 60.0;
-    } else if (strncmp(units, "minute", since - units) == 0) {
-        *unit_seconds = 60.0;
-    } else if (strncmp(units, "seconds", since - units) == 0) {
-        *unit_seconds = 1.0;
-    } else if (strncmp(units, "second", since - units) == 0) {
-        *unit_seconds = 1.0;
-    } else {
-        return 0;
-    }
-
-    const char *origin = since + strlen(" since ");
-    int y = 0, mo = 0, d = 0, h = 0, mi = 0, s = 0;
-    if (sscanf(origin, "%d-%d-%d %d:%d:%d", &y, &mo, &d, &h, &mi, &s) < 3) {
-        return 0;
-    }
-
-    *origin_year = y;
-    *origin_month = mo;
-    *origin_day = d;
-    *origin_hour = h;
-    *origin_minute = mi;
-    *origin_second = s;
-    return 1;
-}
-
-static int format_time_from_units(char *out, size_t outlen, double value, const char *units) {
-    if (!out || outlen == 0 || !units) return 0;
-
-    double unit_seconds = 0.0;
-    int y = 0, mo = 0, d = 0, h = 0, mi = 0, s = 0;
-    if (!parse_time_units(units, &unit_seconds, &y, &mo, &d, &h, &mi, &s)) {
-        return 0;
-    }
-
-    struct tm origin_tm = {0};
-    origin_tm.tm_year = y - 1900;
-    origin_tm.tm_mon = mo - 1;
-    origin_tm.tm_mday = d;
-    origin_tm.tm_hour = h;
-    origin_tm.tm_min = mi;
-    origin_tm.tm_sec = s;
-
-    time_t origin_time = timegm(&origin_tm);
-    if (origin_time == (time_t)-1) return 0;
-
-    double total_seconds = value * unit_seconds;
-    time_t target_time = origin_time + (time_t)llround(total_seconds);
-    struct tm result_tm;
-    if (!gmtime_r(&target_time, &result_tm)) return 0;
-
-    if (result_tm.tm_hour == 0 && result_tm.tm_min == 0 && result_tm.tm_sec == 0) {
-        return strftime(out, outlen, "%Y-%m-%d", &result_tm) > 0;
-    }
-
-    return strftime(out, outlen, "%Y-%m-%d %H:%M:%S", &result_tm) > 0;
-}
-
 static void render_frame(int show_help, int animating) {
     if (!view || !current_var) return;
 
@@ -519,7 +445,7 @@ static void render_frame(int show_help, int animating) {
                     strncpy(time_stamp, formatted, sizeof(time_stamp) - 1);
                     time_stamp[sizeof(time_stamp) - 1] = '\0';
                 } else if (current_dim_info[i].units[0]) {
-                    snprintf(time_stamp, sizeof(time_stamp), " %.6g %s",
+                    snprintf(time_stamp, sizeof(time_stamp), " %.6g %.44s",
                              v, current_dim_info[i].units);
                 } else {
                     snprintf(time_stamp, sizeof(time_stamp), " %.6g", v);
@@ -930,29 +856,44 @@ static void cleanup_all(void) {
 }
 
 static int parse_options(int argc, char **argv, int *first_data_arg) {
+    /* Long-only option codes (above ASCII range to avoid conflicts) */
+    enum {
+        OPT_CHARS = 256,
+        OPT_COLOR,
+        OPT_NO_COLOR,
+        OPT_RENDER,
+        OPT_BOX,
+        OPT_POLAR,
+        OPT_CUTOFF,
+        OPT_YAC,
+        OPT_YAC_METHOD,
+        OPT_YAC_3D,
+    };
+
     static struct option long_options[] = {
         {"mesh", required_argument, 0, 'm'},
         {"resolution", required_argument, 0, 'r'},
         {"influence", required_argument, 0, 'i'},
         {"delay", required_argument, 0, 'd'},
-        {"chars", required_argument, 0, 1000},
-        {"render", required_argument, 0, 1003},
-        {"color", no_argument, 0, 1001},
-        {"no-color", no_argument, 0, 1002},
-        {"box",    required_argument, 0, 1200},
-        {"polar",  required_argument, 0, 1201},
-        {"cutoff", required_argument, 0, 1202},
+        {"chars", required_argument, 0, OPT_CHARS},
+        {"render", required_argument, 0, OPT_RENDER},
+        {"color", no_argument, 0, OPT_COLOR},
+        {"no-color", no_argument, 0, OPT_NO_COLOR},
+        {"box",    required_argument, 0, OPT_BOX},
+        {"polar",  required_argument, 0, OPT_POLAR},
+        {"cutoff", required_argument, 0, OPT_CUTOFF},
 #ifdef HAVE_YAC
-        {"yac",          no_argument,       0, 1099},
-        {"yac-method", required_argument, 0, 1100},
-        {"yac-3d", no_argument, 0, 1101},
+        {"yac",          no_argument,       0, OPT_YAC},
+        {"yac-method", required_argument, 0, OPT_YAC_METHOD},
+        {"yac-3d", no_argument, 0, OPT_YAC_3D},
 #endif
+        {"threads", required_argument, 0, 't'},
         {"help", no_argument, 0, 'h'},
         {0, 0, 0, 0}
     };
 
     int opt;
-    while ((opt = getopt_long(argc, argv, "m:r:i:d:h", long_options, NULL)) != -1) {
+    while ((opt = getopt_long(argc, argv, "m:r:i:d:t:h", long_options, NULL)) != -1) {
         switch (opt) {
             case 'm':
                 strncpy(options.mesh_file, optarg, MAX_NAME_LEN - 1);
@@ -971,11 +912,11 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
             case 'h':
                 print_usage(argv[0]);
                 return 1;
-            case 1000:
+            case OPT_CHARS:
                 strncpy(options.glyph_ramp, optarg, sizeof(options.glyph_ramp) - 1);
                 options.glyph_ramp[sizeof(options.glyph_ramp) - 1] = '\0';
                 break;
-            case 1003: {
+            case OPT_RENDER: {
                 int mode = TERM_RENDER_ASCII;
                 if (term_parse_render_mode(optarg, &mode) != 0) {
                     fprintf(stderr, "Invalid render mode: %s (use ascii|half|braille)\n", optarg);
@@ -984,17 +925,17 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
                 options.render_mode = mode;
                 break;
             }
-            case 1001:
+            case OPT_COLOR:
                 options.color_mode = 1;
                 break;
-            case 1002:
+            case OPT_NO_COLOR:
                 options.color_mode = 0;
                 break;
 #ifdef HAVE_YAC
-            case 1099:
+            case OPT_YAC:
                 options.yac_method = (int)YAC_METHOD_AVERAGE_ARITH;
                 break;
-            case 1100: {
+            case OPT_YAC_METHOD: {
                 USYacMethod ym;
                 if (yac_method_parse(optarg, &ym) != 0) {
                     fprintf(stderr, "Unknown YAC method: %s\n", optarg);
@@ -1005,13 +946,13 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
                 options.yac_method = (int)ym;
                 break;
             }
-            case 1101:
+            case OPT_YAC_3D:
                 options.yac_3d = 1;
                 if (options.yac_method < 0)
                     options.yac_method = (int)YAC_METHOD_AVERAGE_ARITH;
                 break;
 #endif
-            case 1200: {
+            case OPT_BOX: {
                 double w, e, s, n;
                 if (sscanf(optarg, "%lf,%lf,%lf,%lf", &w, &e, &s, &n) != 4) {
                     fprintf(stderr, "Invalid --box format, use W,E,S,N (e.g. -10,30,35,70)\n");
@@ -1023,7 +964,7 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
                 options.target_config.lat_max = n;
                 break;
             }
-            case 1201:
+            case OPT_POLAR:
                 if (strcmp(optarg, "north") == 0) {
                     options.target_config.projection = PROJ_LAEA_NORTH;
                 } else if (strcmp(optarg, "south") == 0) {
@@ -1033,9 +974,18 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
                     return -1;
                 }
                 break;
-            case 1202:
+            case OPT_CUTOFF:
                 options.target_config.cutoff_lat = atof(optarg);
                 break;
+            case 't': {
+                int nt = atoi(optarg);
+                if (nt < 1) {
+                    fprintf(stderr, "Invalid --threads value: %s (must be >= 1)\n", optarg);
+                    return -1;
+                }
+                options.user_threads = nt;
+                break;
+            }
             default:
                 print_usage(argv[0]);
                 return -1;
@@ -1048,6 +998,9 @@ static int parse_options(int argc, char **argv, int *first_data_arg) {
         return -1;
     }
 
+    /* Apply thread settings: CLI > OMP_NUM_THREADS > default 4 */
+    apply_thread_settings(options.user_threads);
+
     *first_data_arg = optind;
     return 0;
 }
diff --git a/src/view.h b/src/view.h
index 9f49ac0..e6960cd 100644
--- a/src/view.h
+++ b/src/view.h
@@ -5,7 +5,7 @@
 #ifndef VIEW_H
 #define VIEW_H
 
-#include "ushow.defines.h"
+#include "us_types.h"
 
 /*
  * Create view for displaying data.
diff --git a/tests/Makefile b/tests/Makefile
index c83fb6f..019f7dd 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -14,7 +14,7 @@ NETCDF_LIBDIR := $(shell $(NC_CONFIG) --prefix 2>/dev/null)/lib
 NETCDF_RPATH := -Wl,-rpath,$(NETCDF_LIBDIR)
 
 CFLAGS += $(NETCDF_CFLAGS)
-LIBS = $(NETCDF_LIBS) $(NETCDF_RPATH) -lm
+LIBS = $(NETCDF_LIBS) $(NETCDF_RPATH) -lm -lpthread
 
 # Zarr support (optional) - build with: make WITH_ZARR=1
 ifdef WITH_ZARR
diff --git a/tests/test_colormaps.c b/tests/test_colormaps.c
index e14ef1c..e11ceff 100644
--- a/tests/test_colormaps.c
+++ b/tests/test_colormaps.c
@@ -3,7 +3,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/colormaps.h"
 #include <stdlib.h>
 #include <string.h>
diff --git a/tests/test_file_grib.c b/tests/test_file_grib.c
index b2ce541..2028e9f 100644
--- a/tests/test_file_grib.c
+++ b/tests/test_file_grib.c
@@ -5,7 +5,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 
 #ifdef HAVE_GRIB
 
diff --git a/tests/test_file_mitgcm.c b/tests/test_file_mitgcm.c
index fb01205..09f0fbd 100644
--- a/tests/test_file_mitgcm.c
+++ b/tests/test_file_mitgcm.c
@@ -6,7 +6,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/file_mitgcm.h"
 #include "../src/mesh.h"
 #include <stdlib.h>
diff --git a/tests/test_file_netcdf.c b/tests/test_file_netcdf.c
index 26b409f..78bb9f7 100644
--- a/tests/test_file_netcdf.c
+++ b/tests/test_file_netcdf.c
@@ -4,7 +4,7 @@
 
 #include "test_framework.h"
 #include "test_utils.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/file_netcdf.h"
 #include "../src/mesh.h"
 #include <stdlib.h>
diff --git a/tests/test_file_zarr.c b/tests/test_file_zarr.c
index 53dbd98..c369cb8 100644
--- a/tests/test_file_zarr.c
+++ b/tests/test_file_zarr.c
@@ -5,7 +5,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 
 #ifdef HAVE_ZARR
 
diff --git a/tests/test_integration.c b/tests/test_integration.c
index d7a70d9..b5b31bd 100644
--- a/tests/test_integration.c
+++ b/tests/test_integration.c
@@ -6,7 +6,7 @@
 
 #include "test_framework.h"
 #include "test_utils.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid.h"
 #include "../src/colormaps.h"
diff --git a/tests/test_latband.c b/tests/test_latband.c
index c454a51..14c0904 100644
--- a/tests/test_latband.c
+++ b/tests/test_latband.c
@@ -9,7 +9,7 @@
 #include "test_framework.h"
 #define _USE_MATH_DEFINES
 #include <math.h>
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/healpix.h"
 #include <stdlib.h>
diff --git a/tests/test_mesh.c b/tests/test_mesh.c
index 38444ac..29e1016 100644
--- a/tests/test_mesh.c
+++ b/tests/test_mesh.c
@@ -6,7 +6,7 @@
 #include "test_utils.h"
 #define _USE_MATH_DEFINES
 #include <math.h>
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include <stdlib.h>
 
diff --git a/tests/test_projection.c b/tests/test_projection.c
index eb206fb..e7a5d84 100644
--- a/tests/test_projection.c
+++ b/tests/test_projection.c
@@ -5,7 +5,7 @@
 #include "test_framework.h"
 #define _USE_MATH_DEFINES
 #include <math.h>
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid.h"
 #include "../src/projection.h"
diff --git a/tests/test_regional_range.c b/tests/test_regional_range.c
index 41d26c3..ee6e77a 100644
--- a/tests/test_regional_range.c
+++ b/tests/test_regional_range.c
@@ -8,7 +8,7 @@
 
 #include "test_framework.h"
 #include "test_utils.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid.h"
 #include "../src/file_netcdf.h"
diff --git a/tests/test_regrid.c b/tests/test_regrid.c
index a47c219..eff5d92 100644
--- a/tests/test_regrid.c
+++ b/tests/test_regrid.c
@@ -5,7 +5,7 @@
 #include "test_framework.h"
 #define _USE_MATH_DEFINES
 #include <math.h>
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid.h"
 #include <stdlib.h>
diff --git a/tests/test_timeseries.c b/tests/test_timeseries.c
index 57858df..6265973 100644
--- a/tests/test_timeseries.c
+++ b/tests/test_timeseries.c
@@ -7,7 +7,7 @@
 
 #include "test_framework.h"
 #include "test_utils.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/file_netcdf.h"
 #include "../src/mesh.h"
 #include <stdlib.h>
diff --git a/tests/test_yac_3d.c b/tests/test_yac_3d.c
index a76b024..11924cd 100644
--- a/tests/test_yac_3d.c
+++ b/tests/test_yac_3d.c
@@ -8,7 +8,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid_yac.h"
 #include <stdlib.h>
diff --git a/tests/test_yac_click.c b/tests/test_yac_click.c
index 45b9aac..4c0efac 100644
--- a/tests/test_yac_click.c
+++ b/tests/test_yac_click.c
@@ -10,7 +10,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/kdtree.h"
 #include "../src/regrid_yac.h"
diff --git a/tests/test_yac_curve2d.c b/tests/test_yac_curve2d.c
index f15072d..5eb9412 100644
--- a/tests/test_yac_curve2d.c
+++ b/tests/test_yac_curve2d.c
@@ -9,7 +9,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/regrid_yac.h"
 #include <stdlib.h>
diff --git a/tests/test_yac_regional.c b/tests/test_yac_regional.c
index e921642..5e449eb 100644
--- a/tests/test_yac_regional.c
+++ b/tests/test_yac_regional.c
@@ -11,7 +11,7 @@
  */
 
 #include "test_framework.h"
-#include "../src/ushow.defines.h"
+#include "../src/us_types.h"
 #include "../src/mesh.h"
 #include "../src/projection.h"
 #include "../src/regrid_yac.h"