diff --git a/dirtools.py b/dirtools.py
index e9f9c98..d5a683b 100644
--- a/dirtools.py
+++ b/dirtools.py
@@ -353,18 +353,19 @@ def to_json(self, base_path='.', dt=None, fmt=None):
             fmt = '{0}@{1}.json'
         if dt is None:
             dt = datetime.utcnow()
+            dt = dt.isoformat().replace(':','-')
         path = fmt.format(self._dir.path.strip('/').split('/')[-1],
-                          dt.isoformat())
+                          dt)
         path = os.path.join(base_path, path)
 
-        with open(path, 'wb') as f:
+        with open(path, 'w') as f:
             f.write(json.dumps(self.state))
 
         return path
 
     @classmethod
     def from_json(cls, path):
-        with open(path, 'rb') as f:
+        with open(path, 'r') as f:
             return cls(state=json.loads(f.read()))