YYDDD is a compact Julian date format that stores a calendar date as a two-digit year followed by the day number within that year.
The YYDDD format consists of two parts: YY for the last two digits of the year, and DDD for the day number within that year.
These examples show how normal Gregorian dates are represented as YYDDD values.
| Gregorian Date | YYDDD |
|---|---|
| 2025-01-01 | 25001 |
| 2025-06-01 | 25152 |
| 2025-12-31 | 25365 |
| 2024-02-29 | 24060 |
To convert a Gregorian date to YYDDD, take the last two digits of the year and append the day number within that year.
25.25 and 152 to get 25152.To convert a YYDDD value back to a Gregorian date, extract the year and the day number. For example, 25152 means year 2025 and day 152, which is 2025-06-01.
For automation or large datasets, use the Bulk Converter on JulianDate.net to convert multiple YYDDD values at once.
If cell A2 contains a valid Excel date, this formula returns a 5-digit YYDDD value:
=TEXT(MOD(YEAR(A2),100),"00")&TEXT(A2-DATE(YEAR(A2),1,0),"000")Some Excel regional settings use semicolons instead of commas. If needed, replace commas with semicolons in the formula.
YYDDD dates are often used when compact numeric date values are easier to store, export or compare than full calendar dates.
Need to convert a single date, a YYDDD value, or hundreds of rows from Excel? Use the free Julian Date Converter and Bulk Converter on JulianDate.net.