Date & Time
Day of Year Calculator – Ordinal Date (1–366) & Reverse
Find the day-of-year number for any date, or convert a year plus day number back to a calendar date. Handles leap years automatically.
Day of year (1–365 or 366)
The ordinal day counts January 1 as day 1 and December 31 as day 365 (or 366 in a leap year). Handy for astronomy, agriculture, and compact date codes.
You can also jump from year + day number → calendar date.