Convert a Date to a Julian Day

Need to convert a calendar date to its Julian Day Number? The Convert a Date to a Julian Day Tool takes any standard YYYY-MM-DD formatted date and returns its Julian Day (JDN) the continuous count of days since January 1, 4713 BCE. Whether you’re working with astronomy, historical data, or scientific records, this tool gives you accurate results instantly.

You can paste one or more dates, import from a file, and export the results.

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 calendar date per line in YYYY-MM-DD format in the Input Calendar Dates box.
  2. Or click Choose File to upload a .txt, .csv, or .log file.
  3. The tool will convert each date to its Julian Day Number and show the results in the Julian Day Numbers box.
  4. Use Copy Output to copy results or Export to File to save them.
  5. Click Clear All to reset everything.

What Convert a Date to a Julian Day Tool can do:

  • Converts valid Gregorian or proleptic Julian dates into Julian Day Numbers
  • Processes multiple dates at once
  • Flags invalid date entries clearly
  • Supports text input and file upload
  • Provides total line count, live updates, copy, and export

Example:

Input:

2000-01-01
2023-11-01
1582-10-15
1900-01-01
2024-03-01

Output:

2000-01-01 → JD 2451545
2023-11-01 → JD 2460259
1582-10-15 → JD 2299161
1900-01-01 → JD 2415021
2024-03-01 → JD 2460371

Common Use Cases:

This tool is ideal for scientists, developers, historians, or educators who need to work with precise time calculations, astronomical models, or calendar conversions. It saves you from manually applying formulas and delivers consistent, accurate Julian Day Numbers in seconds.

Useful Tools & Suggestions:

If you’re flipping formats, Convert a Julian Day to a Date lets you bring everything back to a readable form. And when you’re working with different systems, Convert Gregorian Calendar to Julian Calendar helps bridge the gap.

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