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 September 22, 2026

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.

Calculate with code

These short examples use the same inputs and core calculation as this tool. Adapt validation and formatting to your application.

JavaScript

const birth = new Date('2000-01-15T00:00:00Z');
const today = new Date('2026-01-20T00:00:00Z');
let years = today.getUTCFullYear() - birth.getUTCFullYear();
if (today.getUTCMonth() < birth.getUTCMonth() || (today.getUTCMonth() === birth.getUTCMonth() && today.getUTCDate() < birth.getUTCDate())) years--;
console.log(years); // 26 complete years

TypeScript

const birth = new Date('2000-01-15T00:00:00Z');
const today = new Date('2026-01-20T00:00:00Z');
let years: number = today.getUTCFullYear() - birth.getUTCFullYear();
if (today.getUTCMonth() < birth.getUTCMonth() || (today.getUTCMonth() === birth.getUTCMonth() && today.getUTCDate() < birth.getUTCDate())) years--;
console.log(years); // 26 complete years

Python

from datetime import date
birth, today = date(2000, 1, 15), date(2026, 1, 20)
years = today.year - birth.year - ((today.month, today.day) < (birth.month, birth.day))
print(years)  # 26 complete years

Java

var birth = java.time.LocalDate.of(2000, 1, 15);
var today = java.time.LocalDate.of(2026, 1, 20);
System.out.println(java.time.Period.between(birth, today).getYears()); // 26

var birth = new DateOnly(2000, 1, 15);
var today = new DateOnly(2026, 1, 20);
int years = today.Year - birth.Year - (today < birth.AddYears(today.Year - birth.Year) ? 1 : 0);
Console.WriteLine(years); // 26