DST Analysis Fortran Program

🌍 Overview

This repository contains a Fortran-based program that calculates solar timing parameters such as sunrise, sunset, sunlight duration, and working hours in darkness for multiple cities over a multi-year period. The program is designed to assist in analyzing Daylight Saving Time (DST) effectiveness and solar-work alignment across various geographic regions.

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📊 Key Features

• Calculates:
  • Sunrise & Sunset Times
  • Sunlight Duration
  • Nighttime Duration
  • Working Time in Darkness
• Supports multiple cities and multi-year periods
• Outputs results to CSV format for easy integration with spreadsheet and plotting tools
• Compatible with Windows, tested with gfortran

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📁 Repository Structure

├── dst_analysis.f90        # Main Fortran source code
├── cities.csv              # Input file: list of cities with coordinates
├── output.csv              # Output file: processed daily results
├── summary.csv             # Output file: processed annual results
├── README.md               # Documentation
├── LICENCE.md              # Licence Doc

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📥 Input Format

cities.csv

This file lists the cities and their geographic coordinates in the following format:

  CITY,LATITUDE,LONGITUDE
  ANTALYA,36.9,30.7
  ANKARA,39.9,32.9
  ...

• CITY: Name of the city (string)
• LATITUDE: Latitude in decimal degrees (north = positive)
• LONGITUDE: Longitude in decimal degrees (east = positive)

dst_analysis.f90

Edit the Set run periods and Work periods for a day sections in the main code:

Variable	Type	Description
START_YEAR	integer	Start year of the run period
END_YEAR	integer	End year of the run period
FIRST_TIMEZONE	real	First value of the time zone for analysis
LAST_TIMEZONE	real	Last value of the time zone for analysis
TIMEZONE_STEP	real	Time zone period increment value
TOT_WORKING_HOURS	real	Total working hours in a day
FST_STRT_WORKING_HOURS_HH	real	Hours value of the first start time for the daily work period
FST_STRT_WORKING_HOURS_MM	real	Minutes value of the first start time for the daily work period
LAST_STRT_WORKING_HOURS_HH	real	Hours value of the last end time for the daily work period
LAST_STRT_WORKING_HOURS_MM	real	Minutes value of the last end time for the daily work period
WORKING_HOURS_START_STEP_VALUE	real	Step value for daily work period starting time

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📤 Output Format

output.csv

Each row contains the analyzed DST-related daily data for a specific date and city such as:

  CITY,TIMEZONE,YEAR,MONTH,DAY,TOT_WORKING_HOURS,STR_SRT,STR_SST,STR_SWH,STR_EWH,STR_WORKINDARK,STR_SLD,STR_NTD
  ANTALYA,  2.0,2024, 1, 1,  9.00,07:10:02,16:50:27,07:00:00,16:00:00,00:09:59,09:40:26,14:19:34
  ANTALYA,  2.0,2024, 1, 2,  9.00,07:10:12,16:51:13,07:00:00,16:00:00,00:09:59,09:41:01,14:18:59
  ...
  ANKARA,  2.5,2025, 7,24,  9.00,05:09:52,19:40:20,08:30:00,17:30:00,00:00:00,14:30:28,09:29:32
  ...

• CITY: Name of the city (string)
• TIMEZONE: UTC Timezone (real number)
• YEAR, MONTH, DAY: Date values
• TOT_WORKING_HOURS: Total working hours in a day (real number)
• STR_SRT, STR_SST: Daily sunrise and sunset time
• STR_SWH, STR_EWH: Daily working period start and end time
• STR_WORKINDARK: Daily time of working period in darkness
• STR_SLD, STR_NTD: Daily sunlight and nighttime duration

summary.csv

Each row contains the analyzed DST-related annual data for a specific date and city such as:

 CITY,TIMEZONE,YEAR,STR_SWH,STR_EWH,STR_TOTAL_WORKINDARK
 ANTALYA,  2.0,2024,07:00:00,16:00:00,5:40:59  
 ANTALYA,  2.0,2025,07:00:00,16:00:00,5:31:59  
 ...
 ANKARA,  3.0,2026,09:00:00,18:00:00,38:41:00 
 ...

• CITY: Name of the city (string)
• TIMEZONE: UTC Timezone (real number)
• YEAR: Year values
• STR_SWH, STR_EWH: Daily working period start and end time
• STR_TOTAL_WORKINDARK: Total annual hours of working period in darkness

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⚙️ How to Compile and Run

📌 Requirements

• Fortran compiler (e.g., gfortran)

🧵 Compile

gfortran -o dst_analysis dst_analysis.f90

▶️ Run

./dst_analysis

The program will:

1. Read cities.csv

2. Process each city over multiple years

3. Save the results to output.csv and summary.csv

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📈 Use Cases

The program can be used in its current form or with minor modifications for the following purposes:

• Analyzing DST policies across countries or time zones
• Estimating seasonal variation in solar work alignment
• Urban energy planning or lighting optimization
• Scientific research in solar geometry, climatology, or human productivity

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🧠 Background and Developer Note

This program was developed by Emre Çalıova during undergraduate studies at Istanbul Technical University (ITU) as part of a research project investigating the impacts of Turkey's permanent daylight saving time (DST) policy. This program has been updated and provided for the GitHub repository. It may differ from the program used in the research.

In 2016, Turkey adopted permanent DST to make better use of daylight throughout the year. This policy shift raised public and academic interest, particularly regarding its implications on energy consumption, human circadian rhythms, and daily life schedules. Accurate computation of sunrise and sunset times became essential for these assessments.

This program was created to support daylight saving time assessments by providing precise sun position calculations and darkness during working hours based on geographic and temporal inputs.

The solar position calculations are based on methods from:

• U.S. NOAA Solar Calculator
• Astronomical Algorithms by Jean Meeus

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👨‍💻 Author

Emre Çalıova
Meteorological Engineer

📧 Mail
🔗 LinkedIn
📅 Created: 12.06.2016
📅 Updated: 04.08.2025 (for GitHub Repository)

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📄 License

This project is licensed under the MIT License.

You may use, modify, and distribute it freely. Please credit the author where appropriate.