A familiar situation
Für Formulare, Jubiläen oder die Planung eines Geburtstags lässt sich das Alter an einem beliebigen Stichtag ermitteln.
How to use this calculator
- Enter birth date, age on date.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How age is calculated
Find a person’s completed age between two calendar dates. Calendar anniversaries are compared in UTC, so daylight-saving changes cannot add or remove a day. The result also reports elapsed days and the next birthday; a February 29 birthday is observed on March 1 in non-leap years. For a birth date of 2000-05-10 and a date of 2025-05-09, the completed age is 24; one day later it becomes 25. The calculation validates each input and keeps its stated units explicit. This calculator uses March 1 when the year has no February 29. Local legal conventions can differ. This is an estimate for the stated assumptions; confirm measurements and any applicable professional or local standards before relying on it.
completed years = year difference adjusted for whether the anniversary has occurredFor a birth date of 2000-05-10 and a date of 2025-05-09, the completed age is 24; one day later it becomes 25.
Assumptions & useful context
The result depends on the values you enter and the method described above. Displayed numbers may be rounded; calculations use the unrounded values. Check that this model matches your situation before relying on it.
Frequently asked questions
Why can the birthday fall on March 1?
This calculator uses March 1 when the year has no February 29. Local legal conventions can differ.
Does age include the birth day?
Completed years count anniversaries reached, not inclusive day counts.