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- Converts a calendar date to a Julian date in every common format.
- Shows the day of year, YYDDD, YYYYDDD, YDDD and JD Edwards CYYDDD codes.
- Also gives the astronomical Julian Date (JD) and Modified Julian Date (MJD).
- Works in reverse: type a Julian date and get the calendar date.
How to use the Julian date converter
Choose the direction
Date to Julian turns a normal date into codes. Julian to date reads a code and gives the calendar date.
Enter the date or code
Today is filled in. For a code, pick its format first: YYDDD, YYYYDDD, JD Edwards or astronomical JD.
Add a time if needed
Under advanced options you can set a UTC time. It only changes the astronomical Julian Date.
Copy the format you need
All formats are shown together, so you can use the one your system, label or report needs.
Two kinds of Julian date
The words Julian date mean two different things. In food packaging, the military, logistics and mainframe software, a Julian date is the year plus the day of the year, for example 26310 for the 310th day of 2026. In astronomy, the Julian Date is a running count of days since noon on January 1, 4713 BC, used to measure time between events without calendars getting in the way.
Day-of-year codes
Day of year = days since January 1 + 1
YYDDD = last two digits of the year + day of year with 3 digits
CYYDDD (JD Edwards) = century digit (0 for 1900s, 1 for 2000s) + YY + DDD
Day 310 of 2026 gives 26310, 2026310 and 126310.
Astronomical Julian Date
JDN = Julian Day Number at noon (Fliegel–Van Flandern formula)
JD = JDN − 0.5 + time of day as a fraction of 24 hours (UTC)
MJD = JD − 2,400,000.5
The JD day starts at noon UTC, which is why midnight dates end in .5.
Example: November 6, 2026
A date to every format at 00:00 UTC.
- Day of year 310 of 365
- YYDDD 26310
- YYYYDDD 2026310
- JD Edwards CYYDDD 126310
- Astronomical JD 2461350.5
- MJD 61350.0
The packaging code (YDDD) for the same day is 6310.
Example: reading codes back
Julian to date mode works out the calendar date.
- 24366 December 31, 2024 (leap year, so day 366 exists)
- 126310 November 6, 2026 (JD Edwards)
- 2451545.0 January 1, 2000 at 12:00 UTC (the J2000 reference point)
A code like 25366 is rejected, because 2025 has only 365 days.
Where a Julian date converter helps
Food and product codes
Many cans, eggs and packages print the pack date as a Julian code like 6310 or 26310.
Military and logistics
US military and shipping records often use YYDDD dates in forms and labels.
ERP and mainframes
JD Edwards and older systems store dates as CYYDDD numbers that need converting.
Astronomy
Observers use JD and MJD to time events like variable star brightness and eclipses.
Find the weekday of any date with the day of week calculator, add days with the add days to date calculator, or count the gap between dates with the date difference calculator.
Julian date FAQ
What is today's Julian date?
Open the converter: it fills in today’s date and shows the YYDDD code, day of year and astronomical JD at once.
What does a Julian date like 26310 mean?
The first two digits are the year (2026) and the last three are the day of the year (310). Day 310 of 2026 is November 6.
Is a Julian date the same as the Julian calendar?
No. The Julian calendar is the old calendar Julius Caesar introduced. Julian dates here are counted on the modern Gregorian calendar.
How do I read a JD Edwards date?
Split CYYDDD into C, YY and DDD. C is 0 for the 1900s and 1 for the 2000s. 126310 is 2026, day 310.
Why does the astronomical Julian Date end in .5 at midnight?
Astronomers start each Julian day at noon UTC, so midnight is halfway through the day.
What happens in a leap year?
Leap years have 366 days, so December 31 is day 366. The converter checks this and rejects day 366 in normal years.