Age Calculator
Calculate age in complete years, months and days on a date you choose.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Birth date | Gregorian calendar date in YYYY-MM-DD format; years 0001 through 9999. |
| As-of date | Gregorian calendar date in YYYY-MM-DD format; years 0001 through 9999. |
Understanding your result
Calendar results use the stated counting and anniversary convention. Complete months and years differ from fixed day counts.
Common mistakes
- Counting both end dates when the method excludes a boundary, or assuming all months have equal length.
Check your calculation
- Test a short known interval and a leap-day boundary; for working days, verify your holiday list.
Calculation checks, sources and review limits
How old is someone on a particular date?
Calculate age in complete years, months and days on a date you choose.
Common uses
- Calculate age in complete years, months and days on a date you choose.
How it works
Completed Gregorian years; advance clamped anniversary, then completed clamped months and residual ordinal days. Calendar arithmetic uses the proleptic Gregorian calendar. Explicit calendar dates are independent of local daylight-saving changes. Month/year additions clamp to the last valid day of the destination month. Timestamp arithmetic requires a stated UTC offset and excludes leap seconds.
Worked example
Enter Birth date: 2000-01-15; As-of date: 2024-03-20. The result is Years: 24; Months: 2; Days: 5.
FAQ
How old is someone on a particular date?
Completed Gregorian years; advance clamped anniversary, then completed clamped months and residual ordinal days. Calendar arithmetic uses the proleptic Gregorian calendar. Explicit calendar dates are independent of local daylight-saving changes. Month/year additions clamp to the last valid day of the destination month. Timestamp arithmetic requires a stated UTC offset and excludes leap seconds.
What assumptions and limits apply?
Explicit as-of date and Feb29 convention; avoid automatic browser timezone assumptions.