How Age Is Calculated
The calculator counts complete calendar years between the birth date and the target date (today by default), then counts the remaining months after subtracting those full years, then counts the leftover days. Total days and weeks are calculated as the simple difference in days between the two dates. All calculations account for leap years automatically.
Calculating Age at a Different Date
Uncheck the "Use today" checkbox to enter a custom target date. This lets you calculate how old someone will be on a future date, or how old they were on a historical date.
Frequently Asked Questions
The calculator takes the difference between today's date and your birth date. It counts complete calendar years first, then complete months, then remaining days. This gives you the same result you would get if you counted on a calendar, including accounting for leap years.
If you were born on February 29, the calculator treats March 1 as your birthday in non-leap years for the purpose of counting remaining months and days. Your age in years still increments correctly on the anniversary of your birth year.
The total days figure shown is the exact number of days between your birth date and today, counting every day including leap days. This is sometimes called your Gregorian age in days.
The countdown shows the number of days remaining until your next birthday. If today is your birthday, it shows zero. If your birthday this year has already passed, the countdown targets your birthday in the next calendar year.
Yes. Uncheck the 'Use today' box and enter any target date. The calculator will compute the age or time difference between your birth date and that target date instead of today.
Related Calculators
More tools in the Time & Date category.