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About Julian dates
The words "Julian date" are used for two different things, and this converter does both:
- The day-of-year code (also called an ordinal date): the year and the day of the year, like 26317 for November 13, 2026 (2026, day 317). It is printed on food packs and cans, used in military and government forms, in factories and in older business software.
- The Julian Day (JD) of astronomers: the number of days since noon on January 1, 4713 BC, like 2461358 for the same day. Astronomers and space agencies use it to count days without months and years.
The page opens on today. Pick any date to see both, or switch to YYDDD → date to read a code from a package, or JD → date for a Julian Day number.
Features
- Today's Julian date — the page opens on today's YYDDD and YYYYDDD
- Date → Julian date — YYDDD, YYYYDDD, CYYDDD, day of the year and days left
- Julian date code → date — reads 26317, 2026317, 126317, 2026-001 and short codes
- Julian Day (JD) → date — with the time in UTC, JD or MJD
- Julian Day with time — JD, JDN and Modified Julian Date for any date and UTC time
- Julian calendar date — the same day on the old calendar of Julius Caesar
- Steps and a month table — how the day number is counted
Two different "Julian dates"
| Day-of-year code (ordinal date) | Julian Day (astronomy) | |
|---|---|---|
| Looks like | 26317 or 2026317 | 2461358.0 |
| What it counts | the day of the year (1 to 365, or 366) | days since noon, January 1, 4713 BC |
| Used by | food and drug packs, factories, the military, mainframes | astronomers, satellites, scientists |
| November 13, 2026 | 26317 (YYDDD), 2026317 (YYYYDDD) | 2461358 (at noon UTC) |
Neither has anything to do with the date on the old Julian calendar — see "Julian and Gregorian calendar" below.
How to read a Julian date code
The last three digits are the day of the year: 001 is January 1, 032 is February 1, 365 is December 31 (366 in a leap year). The digits before them are the year.
- YYDDD — two-digit year: 26317 = 2026, day 317 = November 13, 2026
- YYYYDDD — full year: 2026317 = the same day
- CYYDDD — a century digit first (0 = 1900s, 1 = 2000s), used by some business software: 126317
- YDDD — only the last digit of the year, seen on some food packs: 6317. The year has to be guessed — the converter takes the most recent year that ends in that digit.
| Code | Date |
|---|---|
| 26317 | November 13, 2026 |
| 2026317 | November 13, 2026 |
| 126317 | November 13, 2026 |
| 24060 | February 29, 2024 |
| 25365 | December 31, 2025 |
| 27001 | January 1, 2027 |
| 99365 | December 31, 1999 |
To count it yourself, add the days of the months before your date, then the day of the month. For November 13: the days of January to October make 304, and 304 + 13 = 317.
Julian date calendar: the 1st of each month
The day of the year of the 1st of each month. For any other date, add the day of the month and take away 1. From March on, leap years (2028) are one day later.
| Month | Day of year (2026, 2027) | Day of year (leap year: 2028) |
|---|---|---|
| January | 001 | 001 |
| February | 032 | 032 |
| March | 060 | 061 |
| April | 091 | 092 |
| May | 121 | 122 |
| June | 152 | 153 |
| July | 182 | 183 |
| August | 213 | 214 |
| September | 244 | 245 |
| October | 274 | 275 |
| November | 305 | 306 |
| December | 335 | 336 |
The Julian Day Number for astronomers
The Julian Day (JD) counts days in one long line, with no months or years, so the time between two dates is a simple subtraction. Day 0 began at noon on January 1, 4713 BC, a date picked in 1583 by the scholar Joseph Scaliger. A Julian Day starts at noon UTC, not at midnight, so a night of watching the sky stays in one day.
- JD with a time: midnight is .5, noon is .0. 2451545.0 is January 1, 2000 at 12:00 (the J2000 point used in astronomy).
- JDN (Julian Day Number): the whole number for a date, the JD at noon.
- MJD (Modified Julian Date): JD − 2400000.5. It starts at midnight and has smaller numbers.
| Date | JD at 00:00 UTC | JD at 12:00 UTC | MJD at 00:00 UTC |
|---|---|---|---|
| January 1, 1970 (start of Unix time) | 2440587.5 | 2440588.0 | 40587.0 |
| January 1, 2000 (J2000) | 2451544.5 | 2451545.0 | 51544.0 |
| January 1, 2026 | 2461041.5 | 2461042.0 | 61041.0 |
| November 13, 2026 | 2461357.5 | 2461358.0 | 61357.0 |
| January 1, 2027 | 2461406.5 | 2461407.0 | 61406.0 |
The converter counts in UTC. Astronomers sometimes use TT (Terrestrial Time), which runs about one minute ahead of UTC; J2000 is defined in TT.
Julian and Gregorian calendar
The Julian calendar was started by Julius Caesar in 46 BC. It has a leap year every 4 years, which is a little too often. In 1582 Pope Gregory XIII fixed this: Thursday, October 4, 1582 was followed by Friday, October 15, 1582, and years like 1700, 1800 and 1900 were no longer leap years. Many countries changed later — Britain and its colonies in 1752, Russia in 1918.
Today the two calendars are 13 days apart. Some Orthodox churches still use the Julian calendar, so their Christmas on "December 25" falls on January 7. The converter shows the Julian calendar date of every day you pick.
| Gregorian date | Julian calendar date | Difference |
|---|---|---|
| October 15, 1582 | October 5, 1582 | 10 days |
| June 1, 1700 | May 21, 1700 | 11 days |
| June 1, 1800 | May 20, 1800 | 12 days |
| June 1, 1900 | May 19, 1900 | 13 days |
| November 13, 2026 | October 31, 2026 | 13 days |
| June 1, 2100 | May 18, 2100 | 14 days |
Frequently asked questions
What is today's Julian date?
The page opens on today's date and shows it at the top of the result, as YYDDD and YYYYDDD. For example, November 13, 2026 is 26317 (2026317).
How do I read the Julian date on food packaging?
Look for a 4 or 5-digit number. The last three digits are the day of the year, and the digits before them are the year. 25032 means 2025, day 32 = February 1, 2025. Packs may also add a plant or line code, so check what your brand uses.
What Julian date does the military use?
US military forms often use the day-of-year code: YYDDD, or YDDD with only the last digit of the year. The converter reads both.
Is a Julian date the same as the Julian calendar?
No. A Julian date code or Julian Day is a way of counting days. The Julian calendar is the old calendar from before 1582. The converter shows all three.
Why does the Julian Day start at noon?
It was made for astronomers in Europe, who watch the sky at night. With days starting at noon, a whole night has one date.
What is day 366?
December 31 in a leap year (2024, 2028 …). In other years the code ends at 365, and the converter says so.
What is a Modified Julian Date (MJD)?
MJD = JD − 2400000.5. It starts at midnight and uses smaller numbers, so it is easier to read. MJD 60000 was February 25, 2023.
Related tools
- Day of the Week Calculator — the weekday and the day of the year for any date
- Date Calculator — days between two dates, or add days to a date
- Week Number — today's ISO week number and all weeks of a year
- Unix Timestamp Converter — epoch seconds to a date and back
- Military Time Converter — 24-hour time to AM/PM and back
How to use it
- The page opens on today's Julian date — read it at the top of the result
- To convert another day, pick the date (and a time in UTC for the Julian Day)
- To read a code like 26317, choose YYDDD → date and type it
- For an astronomy number like 2451545.0, choose JD → date, and pick JD or MJD
- Read the steps and the month table under the form, or press Copy
