What is YYDDD?
YYDDD uses the last two digits of the year followed by the day number within the year.
Example: the 152nd day of 2025 becomes 25152.
Julian Date Converter
Julian Date Converter
Convert Gregorian, YYDDD and CYYDDD dates instantly.
Built for quick checks, spreadsheets, data work and operational systems.
Converter
Format: YYYY-MM-DD
Results
YYDDD
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CYYDDD
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YYDDD = 2-digit year + day of year •
CYYDDD = century + 2-digit year + day of year
What is CYYDDD?
CYYDDD adds a century digit before the year and day number.
Example: 125152 means century 1, year 25, day 152.
Bulk Converter
Bulk conversion for spreadsheets and larger data sets is planned next. The goal is fast copy/paste conversion for 1000+ rows.
Excel Formulas
A dedicated formulas page is planned with copy/paste Excel examples for Gregorian to YYDDD, Gregorian to CYYDDD, and Julian date back to calendar date.
API-ready
Future versions can include lightweight JSON endpoints for websites, intranets, dashboards and data tools.
Fast by design
JulianDate.net is built as a lightweight utility: fast loading, no account required, and focused on getting the right date value quickly.