Age Calculator

Calculate exact calendar age, complete months and weeks, total days, and the next birthday from a date of birth.

Runs in this browser. No upload by this tool. Dates are not saved by this calculator.

Dates
Use the calendar date of birth.
Defaults to today. Change it to calculate age on another date.

This calculator uses calendar dates only, not times of day. For February 29 births, February 28 is used as the anniversary date in non-leap years for this estimate.

Age result
Enter a date of birth to calculate age.
How this calculation works

Calendar age: the tool counts full years first, then full calendar months from that anniversary, then the remaining calendar days. Month-end dates are clamped to the last valid day of shorter months so results do not produce negative day values.

Total days: the difference is calculated with proleptic Gregorian date-only arithmetic. Time zones and daylight-saving changes are not part of the result.

February 29: in a non-leap year, this calculator treats February 28 as the birthday anniversary for age boundaries and the next-birthday countdown. This is a transparent calculator convention, not a universal legal rule.

Totals: complete months are full calendar months completed; complete weeks are whole seven-day periods; total days is the exact date-only day difference.