How Many Days in a Year?

A regular year has 365 days. A leap year has 366 days, with the extra day added as February 29. The year 2026 is a common year with 365 days. The next leap year is 2028.

The reason we need leap years is that the Earth takes approximately 365.2422 days to orbit the Sun. Without the extra day every four years, the calendar would slowly drift out of alignment with the seasons. After 100 years, the calendar would be off by about 24 days, and eventually summer months would fall in what we think of as winter.

The Gregorian calendar (the one used worldwide today) handles this with a precise rule: a year is a leap year if it is divisible by 4, except for years divisible by 100, unless they are also divisible by 400. So 2000 was a leap year, but 1900 was not, and 2100 will not be either.

📅 Days in Each Month

Mnemonic: "Thirty days has 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."

📅 Leap Years

📅 How Do Leap Years Work?

A leap year has 366 days instead of 365, with the extra day added to February. A year is a leap year if it is divisible by 4, except for century years, which must be divisible by 400. So 2024 was a leap year, 2028 will be, but 1900 was not (divisible by 100 but not 400) and 2000 was (divisible by 400). The next leap years are 2028, 2032, 2036 and 2040.

📅 Why Do We Need Leap Years?

Earth takes 365.2422 days to orbit the Sun, not exactly 365. Without leap years, the calendar would drift by about one day every four years. After a century, summer would start arriving in what the calendar calls August. After 700 years, Christmas would fall in summer. The Gregorian correction (skip 3 leap years every 400 years) keeps the calendar accurate to within one day every 3,236 years.

🌍 Days on Other Calendars and Planets

📅 How Long Is a Year on Other Planets?

A year on Mars is 687 Earth days. A year on Venus is only 225 days, but a Venusian day takes 243 Earth days, making its day longer than its year. Jupiter takes 4,333 Earth days (about 11.86 years) to complete one orbit. If you lived on Neptune, you would wait 165 Earth years for a single birthday.

📅 Do Other Calendars Have 365 Days?

The Islamic calendar has 354 or 355 days (its purely lunar, about 11 days shorter). The Hebrew calendar has 353 to 385 days depending on the year, with an occasional leap month. The Persian calendar has 365 or 366 days like the Gregorian but distributes them across months differently. The old Julian calendar averaged 365.25 days and is now about 13 days behind the Gregorian.

📅 The Year 2000 Was a Leap Year, but 1900 Was Not

Most people know the "divisible by 4" leap year rule, but fewer know the exceptions. Years divisible by 100 are not leap years, unless they are also divisible by 400. So 1900 was not a leap year (divisible by 100 but not 400), but 2000 was (divisible by 400). The next century year that will be a leap year is 2400. This correction keeps the calendar accurate to within one day every 3,236 years.