Age calculator
Calculate age in years, months and days at a chosen reference date.
Your dates and times stay in your browser and are not stored.
Method and assumptions
Method version 1.0.0 · Updated
Age at a date
Formula: Complete calendar months → years + months; remaining days
Gregorian civil dates from years 0001 to 9999, without time or timezone. Monthly anniversaries remain anchored to the birth day, clamped to the last day of shorter months. February 29 becomes February 28 in non-leap years. A calculation convention, not a determination of legal age. Example: January 31 to February 29, 2024 = 0 years, 1 month, 0 days.
- birth
- Date of birth
- reference
- Reference date
Gregorian calendar from years 0001 to 9999. Date, duration and rounding conventions are specified for each mode.