Day of the year calculator
Enter a date to get its day number (1 to 365 or 366), the days remaining and the share of the year that has passed. Or switch mode and enter a year and a day number to get the date.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose A date to get its day number, or A day number to get the date.
- For a date, pick it in the field. For a day number, type the year and the number.
- Read the day of the year, the days left, the length of the year and how much of it has passed.
How it works
The day number is the days between 1 January of that year and the date, plus 1. The year has 366 days if it is a leap year and 365 otherwise; the days left are the year length minus the day number. For the reverse direction, the tool adds the day number minus 1 to 1 January.
Worked example
For 3 November 2026: the ten months before November have 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 = 304 days, plus 3 gives day 307. 2026 has 365 days, so 58 days are left, and 307 / 365 means 84.1 % of the year has passed.
Tips
Remember that after 28 February the day numbers of a leap year are one higher than in a common year: 1 March is day 60 in 2025 and day 61 in 2024.
Frequently asked questions
What is the day of the year?
It is the position of a date in its year, counting 1 January as day 1. In a common year 31 December is day 365, in a leap year it is day 366.
How do I convert a day number to a date?
Switch to "A day number", enter the year and the number. Day 60 is 1 March in a common year but 29 February in a leap year, which is why the year matters.
What is an ordinal date?
It writes a date as the year and the day number, for example 2026-307. ISO 8601 allows this form and it is common in logs, satellite data and some manufacturing codes (often called Julian dates, though they are not the astronomical Julian day).
How are leap years decided?
A year is a leap year if it is divisible by 4, except years divisible by 100, unless they are also divisible by 400. So 2024 and 2000 are leap years, while 2100 and 1900 are not.