Age Calculator
Calculate exact age in years, months, and days from a date of birth.
Enter a date of birth and an optional target date to calculate exact age in years, months, and days, plus the total number of days. Calculated in UTC for consistency.
Enter your date of birth in the first field. The "age at date" field defaults to today, but you can change it to any past or future date to calculate exact age as of that day instead. The result shows the age broken down into years, months, and days, plus the total number of days elapsed — both describe the same span, just in different units.
Formula & methodology
Calendar-aware difference that borrows days from the preceding month and months from the year as needed. UTC-based.
Worked example
- Born 2000-01-15, today 2024-03-10 → 24 years, 1 month, 24 days
Common mistakes
- Expecting a February 29 birthday to "land" on February 28 in non-leap years — the calculator only counts the year as complete once March 1 arrives, so age shown on February 28 will be a month and a day short of a whole year.
- Setting "age at date" to today near midnight in a timezone far from UTC and expecting local time to apply — dates are compared in UTC, so a "today" picked just after local midnight can still fall on the previous UTC day.
- Treating total days and the years/months/days breakdown as two different results — they describe the exact same duration in different units and will never disagree.
Frequently asked questions
How is age counted?
As completed years, months, and days between the two dates, accounting for varying month lengths.
How is age calculated for someone born on February 29?
In leap years the birthday still falls on February 29. In non-leap years the calculator only counts the year as complete once March 1 is reached, so age computed on February 28 will show a month and a day less than a whole year.
Can I calculate age as of a future or past date, not just today?
Yes. Change the "age at date" field to any date, past or future, and the tool recalculates the exact age as of that day instead of today.
Why do the total days and the years/months/days breakdown look inconsistent?
They're not inconsistent — they're the same span in two units. Years/months/days accounts for the differing lengths of months, while total days is a plain day count between the same two dates.
What happens if the target date is earlier than the date of birth?
The target date must be on or after the date of birth; otherwise the calculator shows an invalid date range message.
Which timezone is used for the calculation?
All dates are compared in UTC so the result doesn't change depending on your device's local timezone.
Privacy
All processing happens locally in your browser. Your data is never uploaded.