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Days in Month Calculator.

Find out exactly how many days are in any month of any year, with leap years handled correctly.

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Days in this month: 29 days

Days in this month

29days
2024 is a leap year, so February has 29 days.

Breakdown

MonthFebruary 2024
Leap yearYes
Days in year366

How to Use

A leap year has 366 days instead of 365. A year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400. That is why 1900 was not a leap year but 2000 was.

FAQs

How many days are in February?

February has 28 days in a common year and 29 days in a leap year. The most recent leap year was 2024, and the next is 2028.

Why was 1900 not a leap year but 2000 was?

The Gregorian rule is: a year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400. 1900 is divisible by 100 but not 400, so it had 28 days in February. 2000 is divisible by 400, so it was a leap year. 2100 will not be.

Which months have 31 days?

January, March, May, July, August, October and December have 31 days. April, June, September and November have 30. February has 28 or 29.

How many days are in a year?

A common year has 365 days; a leap year has 366. The long-run Gregorian average is 365.2425 days per year, which is why leap years are skipped in three out of every four century years.

Does this calculator work for dates far in the past?

Yes. It uses the proleptic Gregorian calendar, projecting today's leap-year rules backwards, which is the same convention used by spreadsheets and databases. Note that historical calendars in use before 1582 differed.

Cite this calculator

Canonical URL: https://mathify.one/es/date/days-in-month

Cite as: Mathify. (2026). Calculadora de Días en el Mes. https://mathify.one/es/date/days-in-month

Use Cases

Plan events and schedules

Quickly determine the exact number of days in a specific month for planning projects, billing cycles, or personal events.

Example: Check how many days are in February 2024 to plan a 29-day challenge.

Verify historical dates

Use the calculator to confirm the number of days in a month for historical research or genealogy, especially for century years.

Example: Find out if February 1900 had 28 or 29 days.

Frequently Asked Questions

How does the calculator determine the number of days in a month?
The calculator uses the standard Gregorian calendar rules. For most months, the number of days is fixed (e.g., April has 30 days). For February, it checks if the year is a leap year: divisible by 4, but not by 100 unless also divisible by 400. This correctly handles century years like 1900 (not a leap year) and 2000 (a leap year).
Why does February have 29 days in leap years?
Leap years add an extra day to February to keep the calendar year aligned with the Earth's orbit around the Sun. The rule is: a year is a leap year if it is divisible by 4, except if it is divisible by 100, unless it is also divisible by 400. So 2000 was a leap year, but 1900 was not.
Can I use this calculator for any year, like 2023 or 2100?
Yes, you can enter any year. The calculator applies the Gregorian calendar rules, which are valid for all years in the Gregorian system. For example, 2100 will not be a leap year because it is divisible by 100 but not by 400, so February will have 28 days.

Tips & Common Mistakes

Tips

  • Remember that months with 31 days: January, March, May, July, August, October, December. Months with 30 days: April, June, September, November. February is the only variable month.
  • For leap year checks, remember the rule: divisible by 4, but not by 100 unless also divisible by 400. This means 2000 was a leap year, but 1900 was not.
  • If you're planning for a specific year, double-check the year input to avoid mistakes, especially for century years like 1900 or 2000.
  • Use this calculator for quick reference, but for official purposes, always cross-check with a reliable calendar.

Common Mistakes to Avoid

  • Assuming every year divisible by 4 is a leap year. For example, 1900 is divisible by 4 but is not a leap year because it is divisible by 100 and not by 400.
  • Forgetting that February has 28 days in common years and 29 in leap years. Always verify the year before assuming.
  • Confusing the number of days in months like April (30) and May (31). Use the calculator to avoid memory slips.

Last updated: August 13, 2026