Hack the Hydra
How the age is counted
Full years are counted first, then the remaining full months, then the remaining days. Each month is counted from the same day of the month; when that day does not exist (for example 31 in February), the month ends on the 1st of the next month. For someone born on 29 February, the next birthday in a non-leap year is shown as 1 March, which is how many countries treat it.
Why use an "as of" date
Many forms ask for your age on a given date: the cut-off for a school year, a competition, a pension or insurance rule, or the start of a contract. Enter that date to get the answer without doing the calendar maths by hand. It also works for future dates, such as the age a child will have on the first day of school.
Time zones and precision
Only calendar dates are used, with no time of day, so the result does not change with time zones. Today is read from your device clock. The total days figure is the exact number of calendar days between the two dates.
Example
Age of someone born on 15 May 1990, calculated as of 10 November 2026.
Input
1990-05-15
Output
Age: 36 years, 5 months, 26 days Total: 13,328 days (1,904 weeks) Born on a Tuesday Next birthday: in 186 days (2027-05-15)