How it works
How it is counted
Whole months are counted forward from the start date; remaining days are counted after the last whole month. When the start day does not exist in a month (for example the 31st, or February 29 in a non-leap year), the last day of that month is used, so someone born on February 29 turns a year older on February 28 in non-leap years. Dates are compared as calendar days, so time zones and daylight saving time do not matter. Total days do not include the end date.
Frequently asked questions
How many days are in a year?
365, or 366 in a leap year (years divisible by 4, except century years not divisible by 400).