以下のガイドはまだ日本語に翻訳されていないため、英語で表示しています。計算機自体はすべて日本語に対応しています。
この計算機の使い方
- Enter your date of birth.
- The age is calculated as of today. Change the second date to find your age on any past or future date.
- Results update instantly.
計算式
Age is counted the way people count on a calendar: whole years first, then whole months, then the remaining days. When a month is shorter than your birth day (for example, born on the 31st), the month ends on its last day.
Age = whole years + whole months + remaining days
Total days = date − date of birth
Example
- Born 15 May 1990; age on 8 November 2026.
- Whole years: 36 (to 15 May 2026). Whole months: 5 (to 15 October 2026).
- Remaining days: 24, so the age is 36 years, 5 months and 24 days (13,326 days).
よくある質問
How is age calculated for people born on February 29?
In common years, the birthday is treated as February 28 for counting whole years, which is how date libraries and many legal systems handle it. Some jurisdictions use March 1 instead.
Why do some cultures count age differently?
Traditional East Asian age reckoning counted a newborn as one year old and added a year at the New Year. South Korea officially standardized on the international method in 2023. This calculator uses the international method.
Is my date of birth stored?
No. The calculation runs entirely in your browser.