Age Calculator

Leap years add an extra day (February 29) every 4 years, with exceptions for century years not divisible by 400. A proper age calculator accounts for this by working with actual calendar dates rather than assuming all years have 365 days.

People born on February 29 (leap day) typically celebrate their birthday on February 28 or March 1 in non-leap years. Most age calculators count the birthday as having occurred on February 28 in non-leap years.

Total days lived is the absolute number of days between date of birth and today, accounting for all leap years. It is calculated using the date difference in milliseconds divided by the number of milliseconds in a day (86,400,000).