Last year

when was the last leap year

When was the last leap year is a Gregorian-calendar question. A leap year contains 29 February. The usual rule: a year divisible by 4 is a leap year, except a century year, which is a leap year only when it is also divisible by 400. Under that rule 2000 was a leap year and 1900 was not. 2100 will not be. 2024 divides by 4 and is not a century, so it was a leap year. 2028 will be the next. 2025, 2026, and 2027 are common years: February ends on the 28th.

From any date in 2026, 2025, or 2027, the most recent leap year already finished is 2024. From a date in 2028 after 29 February, the last leap year is 2028 itself. “Last” means the most recent one that has already occurred, not the previous multiple of four if that multiple was skipped. Century exceptions are how people miss 1900 and 2100.

Leap day is a date, not a season. It does not move midsummer. It does not add a week to last year. It adds one civil day to the year that owns it, which makes that year 366 days long instead of 365.

What last year includes

Last year, as a phrase on a form, is the previous numbered year from 1 January through 31 December in the calendar you are using. It does not include “the last twelve months” unless the form said trailing twelve months. Those two spans only coincide on 31 December. On 3 September 2026, last year is still all of 2025. The last twelve months are 3 September 2025 through 2 September 2026, which is a different pile of days.

Tax years, school years, and fiscal years can start in April, July, September, or another month. “Last year” on those documents means the previous complete year of that kind, which may not be last calendar year. Read the heading. A school “last year” can be the academic year that ended in the summer you just had. A tax “last year” can still be open or already filed depending on the authority. Do not mix those labels on one line.

Calendar last year: the previous 1 January–31 December. Trailing twelve months: the year-long span ending today, which crosses New Year except on 31 December. Leap last year: the most recent year that contained 29 February.

Named fiscal or academic last year: whatever that institution’s year is, printed on the form. When you compare “this year” to “last year” in a log, keep the same definition on both sides. A leap year versus a common year is already one day longer. A school year versus a calendar year is a different shape entirely.

Last year does not contain this February, and it does not contain the next 29 February either.

Using last year on a calendar

Weekdays slide. 1 January last year and 1 January this year are usually different days of the week. Recurring meetings copied blindly will land on the wrong weekday. Recurring “last Friday of the month” rules need to be rerun, not copied as dates.

Age in years is not “last year plus one” without a birthday. If the birthday has not arrived yet this year, the completed age is still the age you held on the last birthday, which may sit in last year. The calendar year of birth does not change on 1 January; the completed year-count does, on the anniversary.

When someone asks only “last year” without a noun, they may want the number (2025, if you are in 2026), the leap status of that year (2025 was not a leap year), or a comparison. Give the number first. Add leap status if February is in the conversation. Add fiscal caveats if a form is in the conversation.