Date calculator
Day of Year Calculator
Find which day of the year any date falls on — along with how many days are left in the year and whether it is a leap year. Results are shareable via URL.
Common uses
- Meteorology and climate science — day numbers are used in growing-degree-day calculations
- Data pipelines and log filenames — ordinal day numbers appear in Julian date formats
- Year-progress tracking — see at a glance how far through the year a date falls
- Confirming leap years for date arithmetic or scheduling logic
Related tools
Frequently Asked Questions
What is the day of the year?
The day of the year is the sequential number of a date counting from 1 January. For example, 1 January is day 1, 31 January is day 31, and 31 December is day 365 (or 366 in a leap year).
What is a leap year?
A leap year has 366 days, with 29 February added to the calendar. A year is a leap year if it is divisible by 4, except for century years which must also be divisible by 400. For example, 2000 and 2024 are leap years; 1900 and 2100 are not.
What are common uses for day-of-year numbers?
Day-of-year numbers are used in meteorology, agriculture, aviation, and software development. Scientists use them in growing-degree-day calculations. Developers use them in data pipelines, log filenames, and date arithmetic systems.
Can I share my result?
Yes. Every result has its own URL. Copy it from the address bar or use the Copy URL button.