todayjuliandate
Converter

Converter

Julian Date Converter

Convert in any direction. Enter a calendar date, a day-of-year Julian code, or an astronomical JD/MJD — and see every other representation at once. All conversions run instantly in your browser.

Convert

Enter a calendar date
Calendar date
Julian date (day-of-year)
Astronomical
Julian Date (JD)
Modified JD (MJD)
Julian Day Number
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Every format, from one input

“Julian date” is used for two very different things, so this tool always shows both. When you type a calendar date it produces:

  • YYYYDDD — four-digit year followed by the day of year, e.g. 2026202. The most common form in modern manufacturing and databases.
  • YYDDD — two-digit year plus day of year, e.g. 26202. Common on packaging and legacy mainframes.
  • Day of year (DDD) — the ordinal day, 1–365 or 1–366, on its own.
  • Julian Date (JD) — the astronomical continuous day count, including the fraction of the day from the UTC time you enter.
  • Modified Julian Date (MJD) — JD minus 2,400,000.5.
  • Julian Day Number (JDN) — the integer day beginning at noon UTC.

Decode a Julian date you were given

Switch the input to Julian date (day-of-year) and paste a code from a product label, batch record or report. The converter accepts 7-digit, 5-digit and 3-digit forms and shows the exact calendar date, day of the week, and how far through the year it falls. For a dedicated single-purpose tool, use the Julian date → calendar converter.

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Frequently asked questions

How do I convert a date to a Julian date?

Choose "Calendar date", enter the month, day and year, and the converter instantly shows the day-of-year code (YYYYDDD and YYDDD) plus the astronomical Julian Date, Modified Julian Date and Julian Day Number. To go the other way, switch the input to "Julian date" and paste the code.

Which Julian date format does this converter output?

All of them. For any input it shows the 7-digit YYYYDDD and 5-digit YYDDD day-of-year formats used in industry, the bare day-of-year number, and the astronomical JD, MJD and JDN used in science.

Are my dates sent anywhere?

No. Every calculation happens locally in your browser using JavaScript. Nothing is uploaded, logged or stored.

What date range is supported?

Any year, including BC dates (entered as negative or zero-based astronomical years for the JD scale). The astronomical algorithms follow Jean Meeus and switch between the Julian and Gregorian calendars automatically at the 1582 reform.