Day of the Year Calculator
Pick a date to see its day number, from 1 on 1 January to 365 or 366 on 31 December. It starts as today.
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Formula
day of year = days in the months before + day of the month
days left = days in the year − day of year
A year has 366 days if it divides by 4, except century years that do not divide by 400.
Worked example
1 March 2024: January has 31 days and February has 29 in the leap year 2024, so 31 + 29 + 1 = day 61. The year has 366 days, so 366 − 61 = 305 days remain, and the date is a Friday.
Frequently asked questions
How is the day of the year calculated?
Add up the days in the full months before your date, then add the day of the month. For 1 March 2024 that is 31 + 29 + 1 = day 61.
How many days are in a year?
A common year has 365 days and a leap year has 366. A year is a leap year when it divides by 4, except century years, which must divide by 400, so 2000 was a leap year and 1900 was not.
What day of the year is 31 December?
It is day 365 in a common year such as 2023 and day 366 in a leap year such as 2024.
Is the day of the year the same as an ordinal date?
Yes. An ordinal date writes the year and the day number together, so 1 March 2024 is 2024-061.