What is an ordinal date?
An ordinal date represents a date as a year and a day number within that year.
Date & Time
Ordinal Date Converter
Convert calendar dates to ordinal dates directly in your browser. Find the day of year, convert year and day number back to a date, and handle leap years.
Tool
Ordinal Date Converter
Convert calendar dates to ordinal dates directly in your browser. Find the day of year, convert year and day number back to a date, and handle leap years.
This tool runs in your browser. Your input is processed locally and is not uploaded.
About this Tool
Use this free ordinal date converter to convert a normal date into its day-of-year number. You can also convert a year and ordinal day number back into a calendar date.
Conversion Formula
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An ordinal date is calculated as the day number within the selected year. January 1 is day 1, and the maximum day is 365 in a normal year or 366 in a leap year.
Examples
- 2026-01-01 = day 1 of 2026
- 2026-12-31 = day 365 of 2026
- Convert day 60 of a leap year back to the matching calendar date
Frequently Asked Questions
Is January 1 day 0 or day 1?
In standard ordinal date usage, January 1 is day 1.
Does leap year affect ordinal dates?
Yes. Leap years have 366 days, so dates after February 29 have different day-of-year numbers compared with non-leap years.
Can I convert day of year back to a date?
Yes. Enter a year and day number to calculate the matching calendar date.
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