Days in Month Calculator

Thirty-one, thirty, and February

Pick any month and type any year, and this tool instantly shows how many days that month has. It handles the tricky cases for you: February has 29 days in a leap year and 28 in a common year, while the other months always have their fixed length — 31 days for January, March, May, July, August, October and December, and 30 days for April, June, September and November. Because the day count is computed live from the actual calendar, you get the correct answer for past, present and future dates without memorizing the old "thirty days hath September" rhyme — though "How to remember it" has the rhyme in full, and the knuckle method drawn from the same table. Buttons under the year jump to this year, next year, the next leap year, 2000 and 1900, the two century years the rule treats differently; the year table marks each month long, short or depends on leap year and ends in a "Whole year" total; and Copy link sends the month you are looking at. To list the leap years across a range of years, with how many there are, use the Leap Year Checker.

How leap years are handled

The only month whose length changes is February, and it depends on whether the year is a leap year. Under the Gregorian calendar a year is a leap year when it is divisible by 4, except for century years, which must also be divisible by 400. That is why February 2024 and February 2000 have 29 days, but February 2023 and February 1900 have only 28. This tool applies that rule arithmetically rather than through the browser's built-in date engine, whose constructor quietly remaps years 0–99 into the 1900s — which is why February of year 0 is answered as the 29 days it has and not as 1900's 28. Everything is calculated locally on your device — you can check as many months and years as you like with no limits.