ToolPetal
Julian date converter
- Runs on your device
- Nothing uploaded
- Free, no sign-up
Julian date to calendar date
Codes with a 2-digit or 1-digit year are read as the closest matching year to this one.
How to use the Julian date converter
- Pick a date. It starts on today. The table shows the day of the year, the date codes, the Julian Day Number, the Modified Julian Date and the same day in the old Julian calendar.
- Decode a Julian date. Type it in the second part and choose its type: a date code like 26301, a Julian Day like 2461342.5, or a Modified Julian Date.
- Check short codes. A code like 26301 has only a 2-digit year. It is read as the closest year to the one in Read short years near, so 26301 is 2026 and 98123 is 1998.
Which Julian date do you need?
| Format | Example for October 28, 2026 | Used for |
|---|---|---|
| YYDDD | 26301 | Food and drug packaging, military and government forms, mainframe dates |
| YYYYDDD | 2026301 | Systems that need a 4-digit year |
| YDDD | 6301 | Short lot codes on cans and egg cartons |
| Julian Day Number | 2461342 | Astronomy, counting days between dates |
| Modified Julian Date | 61341 | Satellites, space science and timekeeping |
Worked examples
Date code 24060: year 2024, day 60. 2024 is a leap year, so January has 31 days and February 29, and day 60 is February 29, 2024. In 2025 the same code 25060 is March 1.
Julian Day 2451545.0: the standard astronomy reference point, January 1, 2000 at 12:00 UTC. A Julian Day starts at noon, so the date starts at .5: 2451544.5 is midnight at the start of January 1, 2000.
Modified Julian Date: MJD is the Julian Day minus 2400000.5, so it starts at midnight and has fewer digits. MJD 0 is November 17, 1858.
Day of the year chart
| Month | Common year | Leap year |
|---|---|---|
| January | 001 to 031 | 001 to 031 |
| February | 032 to 059 | 032 to 060 |
| March | 060 to 090 | 061 to 091 |
| April | 091 to 120 | 092 to 121 |
| May | 121 to 151 | 122 to 152 |
| June | 152 to 181 | 153 to 182 |
| July | 182 to 212 | 183 to 213 |
| August | 213 to 243 | 214 to 244 |
| September | 244 to 273 | 245 to 274 |
| October | 274 to 304 | 275 to 305 |
| November | 305 to 334 | 306 to 335 |
| December | 335 to 365 | 336 to 366 |
Leap years are years divisible by 4, except century years not divisible by 400. 2024 and 2028 are leap years, 2100 is not.
Good to know
Dates before October 15, 1582 are shown on the Gregorian calendar extended backwards, as astronomers do. The Julian calendar line shows the same day on the older calendar, which is currently 13 days behind. Julian Day values are in UTC.
Questions
What is a Julian date?
It usually means a date code made of the year and the day of the year, like 26301 for October 28, 2026. In astronomy it means the Julian Day, a count of days since 4713 BC, like 2461342.
How do I read a Julian date code like 24060?
The first two digits are the year and the last three are the day of the year. 24060 is day 60 of 2024, which is February 29, 2024.
What day of the year is it today?
The converter opens on today and shows the day of the year as the first line, with how many days are left in the year.
How do I convert a Julian Day number to a date?
Type the number, choose Julian Day as the type, and the converter shows the date and time in UTC. A Julian Day starts at noon, so 2451545.0 is January 1, 2000 at 12:00 UTC.
What is the difference between Julian Day and Modified Julian Date?
The Modified Julian Date is the Julian Day minus 2400000.5. It starts at midnight instead of noon and is a shorter number.
Is a Julian date the same as the Julian calendar?
No. The Julian calendar is the older calendar replaced by the Gregorian calendar from 1582. It is currently 13 days behind. The converter shows the matching Julian calendar date too.