Day of Year Calculator
Find a date’s ordinal day number within its year.
Results are provided for general informational use. Verify important financial, health or legal figures before relying on them.
About this Day of Year Calculator
The Day of Year Calculator returns the ordinal position of a selected date within its calendar year. It is useful for schedules, datasets, logs and systems that identify dates by a day number rather than month and day.
For related tasks, try Week Number Calculator, Date Difference Calculator or Add Days to Date.
How the calculation works
The tool measures the selected date against January 1 of the same year using UTC-normalized dates to avoid daylight-saving shifts.
How to use it
- Choose a date.
- Select Calculate day number.
- Review the day of year and the number of days in that year.
Practical example
January 1 is day 1. December 31 is day 365 in a normal year and day 366 in a leap year.
Frequently asked questions
Does it account for leap years?
Yes. Leap years have 366 days.
Is January 1 day zero?
No. It is day 1.
Why use day-of-year numbers?
They provide a compact ordinal date often used in technical and scheduling contexts.
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