How the Age Calculator Works
The calculator takes two dates — your date of birth and the date you want to know your age on — and computes the gap in years, months, and days. It handles leap years and varying month lengths, so the result matches how age is reported on official documents and birthday cards (where you're X years old only after the anniversary of your birth has passed).
The Math
It's simpler than it looks. Start by subtracting the birth year from the target year. If the target month/day hasn't reached the birth month/day yet, subtract one from the year and "borrow" from the months. The same borrowing rule applies between months and days, using the actual length of the previous month.
Total Days, Weeks, and Months
Beyond the years/months/days format, the calculator also shows the raw totals: how many days you've been alive, how many weeks, and even how many hours. These figures can be useful for milestone planning (e.g., "10,000 days alive") or just for fun.
Frequently Asked Questions
Does the calculator account for leap years?
Yes — JavaScript's Date object handles leap years natively, so February 29 birthdays calculate correctly even in non-leap years.
What about time zones?
This calculator works at day-level granularity, so time zones don't affect the result unless you're born or measured exactly at midnight near a date boundary. For everyday use, the difference is negligible.