CYYDDD is an extended Julian date format that stores the century, two-digit year and day number within the year in one compact numeric value.
The CYYDDD format consists of three parts: C for the century digit, YY for the last two digits of the year, and DDD for the day number within that year.
1.These examples show how normal Gregorian dates are represented as CYYDDD values.
| Gregorian Date | CYYDDD |
|---|---|
| 2025-01-01 | 125001 |
| 2025-06-01 | 125152 |
| 2025-12-31 | 125365 |
| 2024-02-29 | 124060 |
To convert a Gregorian date to CYYDDD, determine the century digit, take the last two digits of the year, and append the day number within that year.
1.25.1, 25 and 152 to get 125152.To convert a CYYDDD value back to a Gregorian date, extract the century digit, year and day number. For example, 125152 means century 1, year 25 and day 152, which is 2025-06-01.
For automation or large datasets, use the Bulk Converter on JulianDate.net to convert multiple CYYDDD values at once.
If cell A2 contains a valid Excel date, this formula returns a 6-digit CYYDDD value:
=INT((YEAR(A2)-1900)/100)&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.
Both formats use the year and the day number within the year, but CYYDDD adds a century digit at the beginning.
| Format | Example | Meaning |
|---|---|---|
| YYDDD | 25152 | Year 2025, day 152 |
| CYYDDD | 125152 | Century 1, year 25, day 152 |
CYYDDD is commonly seen in JD Edwards and other legacy ERP or operational systems where the century digit is stored as part of the date value.
CYYDDD 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 CYYDDD value, or hundreds of rows from Excel? Use the free Julian Date Converter and Bulk Converter on JulianDate.net.