Age Calculator from Birthday
Enter your date of birth to calculate your exact age in years, months, and days. The calculator also shows the date of your next birthday and how many days away it is. Everything runs locally in your browser.
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How it works
The calculator uses JavaScript's built-in Date object to find the difference between your date of birth and today. It counts complete years first, then remaining months, then remaining days, correctly handling leap years and months of different lengths. Total days are calculated from the raw millisecond difference between the two dates.
Processing runs in your browser
All calculations are pure JavaScript running in your browser tab. Your date of birth is not sent to our servers, stored, or logged at any point.
Related operations
To work out days between any two dates, use the date calculator. For converting between Unix timestamps and human dates, try Unix timestamp. To convert times across zones, see the timezone converter.
Frequently asked questions
- How do I calculate my exact age in years, months, and days?
- Start with the year difference, then adjust for whether this year's birthday has passed. Then count the months, and finally the remaining days. The calculator handles all edge cases including leap years and varying month lengths.
- Why does my age sometimes show 0 months?
- If your birthday falls on the same day or within days of today, the months component may be 0. Your age in years is still shown correctly.
- What day of the week was I born?
- The calculator shows the day of the week for your date of birth alongside your age results.
- Is this calculator accurate for all dates?
- Yes. It uses JavaScript's built-in Date object, which correctly handles all calendar edge cases including leap years and varying month lengths.