How many days are in a year?

A common year has 365 days. A leap year has 366 days (February has 29 days instead of 28). The average calendar year over a 400-year cycle is 365.2425 days.

How do you determine if a year is a leap year?

A year is a leap year if: (1) it is divisible by 4, AND (2) it is NOT divisible by 100, UNLESS (3) it is also divisible by 400. So 2024 is a leap year, 1900 was not, and 2000 was.

Why do we need leap years?

Earth takes approximately 365.2422 days to orbit the Sun. Without leap years, the calendar would drift about 1 day every 4 years. After 100 years, the calendar would be off by 24 days, causing seasons to shift.

How Many Days in a Year? (365/366)

The Quick Answer

A regular year has 365 days. A leap year has 366 days.

Days in Each Month

Month	Days (Regular)	Days (Leap)
January	31	31
February	28	29
March	31	31
April	30	30
May	31	31
June	30	30
July	31	31
August	31	31
September	30	30
October	31	31
November	30	30
December	31	31
Total	365	366

Leap Year Rules

If the year is divisible by 4, it is a leap year.
Exception: if divisible by 100, it is NOT a leap year.
Exception to the exception: if divisible by 400, it IS a leap year.

Examples: 2024 (leap), 2025 (not leap), 1900 (not leap), 2000 (leap).

Year Length Comparison

Year Type	Days	Hours	Seconds
Regular year	365	8,760	31,536,000
Leap year	366	8,784	31,622,400
Tropical year	365.2422	8,765.81	31,556,926

Why It Matters

Knowing the exact number of days matters for financial calculations (interest accrual), project planning, legal deadlines, and software development (date arithmetic). The date calculator handles all of this automatically.