What is a leap year?
A leap year has 366 days instead of 365, with the extra day added as February 29. Leap years occur:
- Every year divisible by 4 (2024, 2028, 2032...)
- EXCEPT years divisible by 100 (1900, 2100...)
- UNLESS the year is divisible by 400 (2000, 2400...)
This rule keeps the calendar aligned with Earth's orbit around the sun (approximately 365.2422 days).
How age is calculated for Feb 29 birthdays
In non-leap years, the anniversary of a February 29 birthday is observed on March 1. This calculator uses March 1 consistently for both age calculation and birthday countdowns:
- In leap years: Your birthday is February 29. On that day, you turn a year older.
- In non-leap years: Your birthday is observed on March 1. Your age increases on March 1.
For example, if you were born on February 29, 2000:
- On February 28, 2026 (non-leap year): You are still 25.
- On March 1, 2026: You turn 26.
- On February 29, 2028 (leap year): You turn 28.
Why March 1 and not February 28?
March 1 is the day after February 28, making it the 60th day of a non-leap year. February 29 is the 60th day of a leap year. Using March 1 preserves your position as the 60th day of the year.
Different jurisdictions use different rules — some use February 28 for certain official purposes. This calculator uses March 1 as the observance date.
Counting days for leap day birthdays
The total number of days you have lived is still exact — the calendar simply counts every day from your birth. The only question is which date you consider your "birthday observance" in non-leap years.
Use the Age Calculator or Next Birthday Calculator with any Feb 29 birth date to see how the math works in practice.