How it works
Compute exact age in years, months, and days from a date of birth.
Enter your date of birth and an optional reference date (defaults to today). The calculator returns your calendar age and the total days and months lived.
Formula
Calendar age is computed from the day, month, and year difference, accounting for month lengths and birthdays not yet reached this year.
birth- Date of birth (date)
asOf- Reference date (optional) (date)
Examples
- Born 15 May 1990, on 15 May 2024Date of birth 1990-05-15 · as of 2024-05-1534 years, 0 months, 0 days · 12,419 total days
Frequently asked questions
How are months and days counted?
As exact calendar units — e.g. a person born on the 10th turns the next month on the 10th of the following month.
What if I don't enter an as-of date?
The calculator uses today's date (UTC), so the result changes slightly from day to day.
How to read the result
Total days counts every calendar day (including leap days). Total months is years × 12 plus the remaining months.
Limitations
Date math uses the Gregorian calendar. It does not account for hours/DST subtleties, which are irrelevant for whole-day age.
Source: Standard Gregorian calendar age calculation.