How do you know if February has 28 or 29 days?

February has 29 days in a leap year and 28 otherwise. A year is a leap year when it is divisible by 4, except for century years (like 1900), which must also be divisible by 400 (so 2000 was a leap year but 1900 was not).

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.

Why does the year matter for the number of days?

The year only changes the answer for February, which has 29 days in a leap year and 28 otherwise. Every other month is the same length in every year, so entering the year mainly affects February and the starting and ending weekdays.

How many days are in a year?

A common year has 365 days and a leap year has 366. The extra day is 29 February, added in years divisible by 4 except century years that are not divisible by 400.

How can I remember the month lengths?

The knuckle trick works: count across the knuckles and dips of a fist — knuckles are 31-day months and the dips between them are the shorter months. There is also the rhyme "Thirty days hath September, April, June, and November".

Is anything sent to a server?

No. The calculation runs entirely in your browser and nothing is uploaded.

What is the Days in Month Calculator?

Find how many days are in any month of any year, including leap-year February, plus the weekday the month starts and ends on. Runs entirely in your browser — nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Days in Month Calculator

Name: Days in Month Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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How many days are in a month?

Pick a month and year to see exactly how many days it has, whether the year is a leap year, and which weekdays the month begins and ends on. It is handy for planning rotas, payroll periods, rent calculations and anyone who needs a quick, accurate month length.

How it works

The tool asks the calendar for the last day of the chosen month — internally, day 0 of the following month, which is the final day of the month you picked. That value is 28, 29, 30 or 31. It also checks whether the year is a leap year (divisible by 4, except century years which must be divisible by 400) and reports the weekday of the first and last day of the month.

Only February changes length: 29 days in a leap year, 28 otherwise. The other eleven months are fixed.

Month lengths at a glance

Month	Days	Always fixed?
January	31	Yes
February	28 or 29	No — depends on leap year
March	31	Yes
April	30	Yes
May	31	Yes
June	30	Yes
July	31	Yes
August	31	Yes
September	30	Yes
October	31	Yes
November	30	Yes
December	31	Yes

Leap year rule in full

A year is a leap year — giving February 29 days — when:

It is divisible by 4, and
If it is a century year (divisible by 100), it must also be divisible by 400.

So 2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400). The next century-year exception after 2000 is 2100, which will be a common year.

Practical uses

Payroll and billing. Some pay periods are calendar-monthly, so the number of working days varies. Knowing that February has only 28 or 29 days versus 31 in longer months matters for prorating salaries, contractor invoices, and SLA calculations.

Rota and shift planning. A nurse planner or a manager building a monthly rota needs to know whether the month has four or five weekends, which depends on which day it starts and how many days it has. The starting and ending weekday the tool reports helps answer this instantly.

Rent and interest proration. Rent is often prorated when a tenant moves in mid-month: (daily rate × days remaining) = (monthly rent ÷ days in month) × days remaining. The days-in-month figure is the key input to that calculation.

Worked example. For February 2024 (a leap year):

Days: 29
First day: Thursday
Last day: Thursday
Leap year: Yes

A rota covering the whole month therefore has exactly 5 Thursdays and 4 of every other weekday. This happens only when February has 29 days and starts on a Thursday.

Everything is calculated locally in your browser.