gizmobench

Age Calculator

Enter a date of birth and get an exact age in years, months and days, plus the total in months, weeks, days and hours, the weekday you were born on, and how long until the next birthday. Leap-day birthdays and anniversaries in short months are both handled properly, which is where most calculators quietly go wrong.

Age calculatorPick a date of birth to see an exact age.
Date of birth
Age at

Common questions

When does someone born on 29 February have their birthday?
In a leap year, on 29 February. In a common year there is no such date, and the two conventions in use disagree by a day. This tool uses the more common one, where the anniversary falls on 1 March, and says so on screen rather than hiding the choice. Someone born on 29 February 2004 turns 21 on 1 March 2025, not 28 February.
What happens when a birthday falls on the 31st of a month that is shorter?
The anniversary is clamped to the last day of that month, so one month after 31 January is 28 February, or 29 February in a leap year. Letting the date overflow to 3 March instead is what produces the negative day counts you sometimes see in other calculators.
Why not just divide the number of days by 365?
Because a year is not a fixed number of days and a month is not a fixed number either. Dividing by 365 or 365.25 drifts by a day around leap years and cannot produce a correct months-and-days breakdown. This calculator works on calendar fields (real month lengths, real leap years) instead of an average.
Is the age counted from midnight?
Yes. Both dates are taken at local midnight so the answer does not change depending on the time of day you load the page. Ages are conventionally counted in whole days, and the hours total is derived from those whole days.
How do I work out an age on a past or future date?
Switch Age at from Today to A set date, and an As of field appears: put the test date, the eligibility date or the anniversary in it and the answer is the age on that day rather than now. Left on Today, the calculation runs against today's date in your own timezone. For the full span between two arbitrary dates, rather than an age, use the duration calculator.
Is my date of birth sent anywhere?
No. The calculation happens in your browser and the date is stored only in your own browser so the page remembers it next time. Nothing is uploaded, which is worth knowing given a date of birth is a common identity-verification field.

Exact, and it states the leap-day convention it used rather than picking one silently.