date-time-tools
Day of Year Calculator
Enter a Gregorian date and calculate its day-of-year number, whether the year is a leap year, total days in the year, and days remaining.
Tool workspace
The interactive tool requires JavaScript.
Instructions
Run the calculation to see the day number, year length, leap-year status, and days remaining.
Before copying the result, confirm that your source system uses the same calendar-day convention.
Use this browser-local calculator for annual progress checks, schedules, log dates, content calendars, and day-of-year fields in data workflows. The calculation stays in your browser and does not upload the date.
Direct answer
The Day of Year Calculator compares the selected date with January 1 of the same year, returns a 1-based day-of-year number, and shows whether the year has 365 or 366 days.
How to use this tool
- Choose or enter a Gregorian date in YYYY-MM-DD format.
- Run the calculation to see the day number, year length, leap-year status, and days remaining.
- Before copying the result, confirm that your source system uses the same calendar-day convention.
How day of year is calculated
The calculator treats January 1 as day 1, then counts calendar days from the start of the year to the selected date.
Leap-year impact
Leap years have 366 days. February 29 shifts March 1 and later dates one day higher than they would be in a common year.
Local date boundaries
The input is date-only. The calculation avoids shifting the chosen date across midnight because of local time zones, daylight saving time, or UTC offsets.
Frequently asked questions
Is January 1 day 0 or day 1?
This tool uses the common 1-based day-of-year convention, so January 1 is day 1.
What day of year is February 29?
In a leap year, February 29 is day 60. Common years do not have February 29.
Does this consider holidays or business days?
No. The result is based on Gregorian calendar days only, not holidays, make-up workdays, company schedules, or regional calendars.
Does the tool upload my date?
No. The calculation runs locally in your browser without an account, backend service, external API, or database.
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