A standard calendar year has 365 days, divided into 12 months. However, every four years (with some exceptions), we add an extra day to keep the calendar aligned with Earth's orbit around the Sun.
Standard Year: 365 Days
In a regular year, the 365 days are distributed across 12 months:
- January: 31 days
- February: 28 days
- March: 31 days
- April: 30 days
- May: 31 days
- June: 30 days
- July: 31 days
- August: 31 days
- September: 30 days
- October: 31 days
- November: 30 days
- December: 31 days
Leap Year: 366 Days
A leap year adds one extra day — February 29 — bringing the total to 366 days. This happens every four years to account for the fact that Earth's orbit around the Sun takes approximately 365.25 days.
Leap Year Rules
A year is a leap year if:
- It is divisible by 4, and
- If divisible by 100, it must also be divisible by 400
Examples: 2024 is a leap year. 2100 will not be (divisible by 100, not by 400). 2000 was a leap year (divisible by 400).
How Does This Affect Date Calculations?
When you calculate how many days until a date, leap years are automatically accounted for. If your countdown crosses February 29 in a leap year, the calculation adds that extra day correctly.
Put It Into Practice
Use our free, instant calculator tools to run these calculations on your exact dates without any manual math.