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Date & age
Age Calculator
Calculate exact age in years, months and days, total days lived, and days until the next birthday.
How to calculate age from a date of birth
Use calendar dates
Enter a date of birth and a reference date. Age is counted in completed birthday years, then completed months from the last birthday, then remaining days. If a month has no matching day, its last day is used. Total days lived is the elapsed number of days between the dates.
Worked example: 15 January 2000
For a birth date of 15 January 2000 and a reference date of 6 September 2026, the result is 26 years, 7 months and 22 days. That interval contains 9,731 elapsed days, with 131 days remaining until 15 January 2027.
Date conventions and limits
Calculations use dates without a birth time or time of day. The birth date must be on or before the reference date. A 29 February birthday is treated as 1 March in a non-leap year for both age and the next-birthday countdown. Formal age requirements may use their own conventions.