Writing and time tools
Age Calculator
Calculate age in years, months and days on any selected date. See total days lived and the next birthday, with explicit leap-day and month-end handling.
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How to use this tool
1. Enter a date of birth and the date to calculate age on. Use today fills the current local date from your device.
2. For a 29 February birth, choose whether the anniversary falls on 28 February or 1 March in a non-leap year.
3. Calculate to see completed years, remaining months and days, total elapsed calendar days and the next birthday. Copy or print the selected dates and result.
Calendar convention
Completed years are counted at each birthday anniversary. Remaining months are counted from the most recent anniversary; each target month keeps its day number where possible and otherwise uses its last day. Remaining days run from that monthly anchor to the selected date.
Worked example
From 15 June 1990 to 7 November 2026, the calendar age is 36 years, 4 months and 23 days. From 31 January to 28 February 2025, the result is 0 years, 1 month and 0 days under the month-end rule.
Questions and assumptions
Leap-day birthdays
For people born on 29 February, the chosen convention determines both completed years and the next birthday in non-leap years. The default is 28 February. This is a calendar utility; legal eligibility rules and cultural age systems may use a different convention.
Dates, birthdays and privacy
Gregorian dates from 1600 through 9999 are supported. The calculation date must be on or after birth. A birthday on the selected date is included as the next birthday, with zero days remaining. Time of birth, time zones and daylight-saving hours are not used. Copy and print include the dates you entered.
Sources and further reading
Built and maintained by Custom Logic. Page updated .