年齢計算
年・月・日単位の正確な年齢と、次の誕生日までの日数を計算します。
すべての計算はブラウザ内で行われます。生年月日がサーバーに送信・保存されることはありません。
結果
使い方
Enter a date of birth. The age is calculated as of today by default; change the reference date to compute an age at any point in time — past or future. Alongside the exact age you get the total in months, weeks and days, the weekday of birth, and how long until the next birthday.
例
- Born 2000-02-29: in common years the birthday anniversary is counted on February 28, so on 2026-02-28 the exact age reads 26 years 0 months 0 days.
- Born 1990-07-26, on 2026-07-26 the age is exactly 36 years 0 months 0 days.
よくある質問
How is “exact age” defined here?
It is the completed years, months and days between the birth date and the reference date — the same convention used on official documents in most countries. You turn a year older on your birthday, not on January 1.
What about people born on February 29?
In common years the next birthday is shown as February 28. The total-days figure is always exact regardless, because it counts real calendar days.
Is my date of birth uploaded anywhere?
No. This page is a static file; the calculation runs entirely in your browser and the date you enter is never transmitted or stored on a server.