Age Calculator
Work out exact age in years, months and days on today or any specific date, plus total days lived and the weekday you were born. Leap-day birthdays handled.
Age on reference date
This calendar convention is stated explicitly; legal age rules can differ by jurisdiction. The reference date cannot precede birth. No birth time or local timezone is included.
Formula checked · NumberSwift · Review process
How this calculator works
Age is decomposed into completed calendar years, then completed months, then remaining days. A February 29 anniversary is treated as February 28 in a non-leap year. Month-end anniversaries are clamped to the last day available in the destination month, so the result never contains negative days.
Formula
Reference date − completed year anniversary − completed month anniversary = remaining days. Total days is a separate exact calendar difference.
Assumptions & limitations
This calendar convention is stated explicitly; legal age rules can differ by jurisdiction. The reference date cannot precede birth. No birth time or local timezone is included.
Sources & reference material
- Date and UTC calendar methods ↗
Calendar arithmetic uses UTC date boundaries, not local elapsed hours.
Worked example
Someone born on 29 February 2000 is 25 years old on 28 February 2025 under this convention. A person born on 20 October 1996 is exactly 30 on 20 October 2026.
Useful next calculations
Choose a related task to continue with the right assumptions:
Common questions
Can I find age on a past date?
Yes. Set Age on date to the reference date you need, provided it is on or after birth.
How are leap-day birthdays handled?
The yearly anniversary is February 28 in years without February 29. This is a calculation convention, not a legal determination.
Why show total days separately?
Years and months vary in length. Total days gives a calendar count that does not rely on a 365-day-year approximation.