The quick answer, the full month-by-month list, the rhyme and knuckle trick for remembering it, why February is the odd one out, and how it all adds up across 2026.
Seven months have 31 days, four have 30, and February has 28.
The long months are January, March, May, July, August, October and December (31 days). The short ones are April, June, September and November (30 days). February has 28 days, or 29 in a leap year.
The full list, month by month
The 31-day months are highlighted. The order never changes from year to year — only February's count moves, between 28 and 29.
Month
Days
Length
January
31
Long month
February
28*
Short — 29 in a leap year
March
31
Long month
April
30
30-day month
May
31
Long month
June
30
30-day month
July
31
Long month
August
31
Long month
September
30
30-day month
October
31
Long month
November
30
30-day month
December
31
Long month
* February has 28 days in a common year and 29 in a leap year. Add it all up and a common year is 365 days (7×31 + 4×30 + 28), while a leap year is 366.
The rhyme: "Thirty days hath September"
The oldest memory aid in English is a short verse that's been passed around since at least the 1500s. It lists the four 30-day months by name, then mops up the rest:
Thirty days hath September,
April, June, and November.
All the rest have thirty-one,
Except February alone,
Which has twenty-eight days clear,
And twenty-nine in each leap year.
If you only remember the first two lines, you've still got what matters: September, April, June and November are the four 30-day months. Everything except those four and February has 31.
The knuckle trick
If rhymes aren't your thing, your hands work just as well. Make a fist and count across the knuckles and the dips between them, left to right:
A knuckle (the raised bumps) means a 31-day month.
A dip (the gaps between knuckles) means a 30-day month — or February.
Start on the first knuckle: January (knuckle, 31) → February (dip, 28) → March (knuckle, 31) → April (dip, 30)… and so on. When you reach the last knuckle at July, jump back to the first knuckle of the same hand (or carry on to your other fist) for August — which is also a knuckle, and that's exactly why July and August are two long months in a row.
Why two 31-day months sit side by side
July and August are both 31 days, which breaks the neat long-short-long pattern. The usual story is Roman: the month we call July was named for Julius Caesar and the next for Augustus, and tradition holds that August was bumped up to 31 days so it wouldn't look shorter than Caesar's month. Whatever the exact history, the result is the small bump you feel on the knuckles — two raised months together at the turn of summer.
Why February is the short one
February drew the short straw because of how the Roman calendar was built. Early versions of it began the year in March and treated the dead of winter almost as an afterthought; February ended up as the month that absorbs the leftover days so every other month can keep a tidy 30 or 31. When the leap day is needed to keep the calendar in step with the seasons, it's tacked onto February too — giving it 29 days roughly every four years.
Common year total = 365 days · Leap year total = 366 days
That's also why a common year is 52 weeks and 1 spare day, and a leap year 52 weeks and 2 — the leftover days that slowly shift which weekday each date lands on, and occasionally push a year to a 53rd ISO week.
Related calendar tools
Once you know how long each month runs, the rest of the counting is easy. To see every date of this year laid out with its week number, open the 2026 week calendar; to count the gap between two dates or add days to one, use the calculators on the week.hako.to home page; and to total only the working days in a stretch, see business days between two dates; and to convert a month into hours, minutes or seconds, see units of time explained.