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Julian Date Calculator

Convert between a calendar date and Julian date code.

Julian date (short)

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Julian date (long)

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What this calculator does

This calculator converts any calendar date into military/manufacturing Julian date format (year + day of year), and can also convert a Julian date code back into a calendar date.

Worked example

September 3, 2026 is day 246 of the year, giving a short Julian date of26246 and a long form of 2026246.

Common mistakes

  • Confusing this with the astronomical Julian Day Number. Astronomers use a continuously counted day number since 4713 BCE — a very different, much larger number than this manufacturing-style code.
  • Forgetting leap years. In a leap year, day 60 is February 29th instead of March 1st, shifting every subsequent day-of-year number by one compared to a non-leap year.

Frequently asked questions

What is a Julian date in this context?+

This is the military and manufacturing style Julian date — a 2-digit year followed by a 3-digit day-of-year number (e.g. 26246 for the 246th day of 2026) — commonly used on food packaging, military logistics, and manufacturing date codes. It is different from the astronomical Julian Day Number used by astronomers.

Why does the day-of-year number matter?+

It lets you encode any date in a year using just 3 digits, from 001 (January 1st) to 365 or 366 (December 31st), instead of a month and day.

How do I read a Julian date code on packaging?+

For a code like 26246: the first 2 digits (26) are the year 2026, and the last 3 digits (246) are the day of that year — September 3rd.

How do you convert a date to a Julian date code?+

Take the last two digits of the year, then append the day of the year as a 3-digit number (with leading zeros if needed). This calculator does that conversion instantly in both directions.

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