Day of the year calculator

Find the day number of a date, or convert a year and day number back to a date.

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Updated 2026-09-20

Using Day of the year calculator

January 1 is day 1. Leap years have 366 days; common years have 365. The ordinal date uses YYYY-DDD, with a three-digit day number. Days remaining excludes the selected date.

A worked example

February 29, 2024 is day 60, written 2024-060. December 31, 2024 is day 366 with no days remaining.

Before you use the result

Ordinal dates are sometimes called Julian dates on labels, but they are different from astronomical Julian dates. Day 366 is only valid in a leap year.

Next: Julian date converter

Next: Leap year calculator

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ToolOctopus. “Day of the year calculator.” Updated 2026-09-20. https://tooloctopus.com/day-of-the-year-calculator.

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