Convert Gregorian Calendar to Julian Calendar

Need to convert modern Gregorian dates into their historical Julian calendar equivalents? The Convert Gregorian Calendar to Julian Calendar Tool does exactly that. Whether you’re working with historical data, religious calendars, or astronomical calculations, this tool quickly translates any list of YYYY-MM-DD formatted dates into the corresponding Julian dates.

It supports bulk input, file import, live conversion, and easy export.

Paste your input above or import a file below.
No file chosen
Supported file types: .txt, .csv, .log
Total dates: 0

How to Use:

  1. Enter one Gregorian date per line in the Input Gregorian Dates box using YYYY-MM-DD format.
  2. Or click Choose File to upload a .txt, .csv, or .log file containing dates.
  3. The converted Julian Calendar Dates will appear instantly to the right.
  4. Use Copy Output to copy the result or Export to File to download it.
  5. Click Clear All to reset everything and start fresh.

What Convert Gregorian Calendar to Julian Calendar Tool can do:

  • Converts any valid Gregorian date to its Julian calendar equivalent
  • Adjusts based on year-specific Gregorian reform differences:
    • 10-day shift around 1582
    • 13-day shift for modern 20th–21st century dates
  • Flags invalid or malformed input lines
  • Supports file upload and multiline entry
  • Live updates with flashing feedback and total count

Example:

Input:

2024-03-01
2000-01-01
1582-10-15
1900-12-31
2023-11-05

Output:

2024-03-01 → 2024-02-17
2000-01-01 → 1999-12-19
1582-10-15 → 1582-10-05
1900-12-31 → 1900-12-18
2023-11-05 → 2023-10-23

Common Use Cases:

This tool is ideal for historians converting post-1582 documents, researchers comparing events between calendar systems, and developers building calendar utilities. It takes care of the complicated logic so you can focus on your work.

Useful Tools & Suggestions:

To undo that shift, Convert Julian Calendar to Gregorian Calendar brings everything back in sync. And if you want to analyze it further, Convert a Date to a Julian Day gives you the numeric version for easy calculations.

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