Day of Year
Find the 1-based day number of a date within its year, from 1 through 365 or 366.
How to use
- Choose a date.
- Calculate.
- Review the day-of-year number and the year's total day count.
Capabilities and scope
Convert a month/day into its ordinal day-of-year value and see whether the containing year is a leap year.
How it works
The implementation measures the UTC calendar-day distance from the boundary immediately before January 1. A leap year therefore has 366 available ordinal days.
Example
January 1 is day 1. December 31 is day 365 in a common year and day 366 in a leap year.
Useful for
- Work with day-of-year datasets
- Check annual progress dates
- Verify leap-year ordinal shifts
Before you use it
- This is a human-facing 1-based ordinal, not a zero-based programming index.
Frequently asked questions
What day of year is February 29?
It is day 60 in a leap year.
Do dates after February shift in leap years?
Yes. After February 29, leap-year ordinal values are one higher than in a common year.