How to use the age calculator
- Enter the date of birth.
- Leave “age as of” on today, or pick another date to find the age on that day.
- Read the exact age in years, months and days, plus totals in months, weeks and days.
- See how many days remain until the next birthday and which weekday it falls on.
Worked example
Born 15 June 1990, age on 25 September 2026
The age is 36 years, 3 months and 10 days, which is 435 months and 10 days, or 13,251 days (exactly 1,893 weeks). The person was born on a Friday. The next birthday, their 37th, is on Tuesday 15 June 2027, 263 days away.
How it works
Whole months are counted as the largest number of calendar months that can be added to the birth date without passing the as-of date; when the birth day does not exist in a month (such as the 31st, or 29 February) the last day of that month is used. The remaining days are counted from there. Total days are the difference between the two dates in UTC calendar days, so time zones and daylight saving never add or remove a day.
Assumptions
- People born on 29 February have their birthday counted on 28 February in non-leap years.
- “Today” uses the date in your own time zone.
Frequently asked questions
How is age calculated for someone born on 29 February?
In non-leap years this calculator treats 28 February as the birthday. Some legal systems use 1 March instead, so check local rules for official purposes.
Why do different age calculators sometimes disagree by a day?
Months have different lengths, so “one month after 31 January” has no single answer. This calculator uses the end of the shorter month, which is the most common convention.
Is my date of birth stored?
No. Everything is calculated in your browser. The Share button puts the dates in the link fragment, which is not sent to our server.
Limitations
- Uses the Gregorian calendar for all dates.
- Does not account for time of birth or time zones of birth.