Working out an exact age sounds simple until months of different lengths and leap years get involved. This calculator takes a date of birth and returns the age in years, months and days, then adds the totals people often want for fun or paperwork: months, weeks, days and hours lived, the date and weekday of the next birthday, and the day of the week you were born.
By default it measures age as of today, but you can pick any other date, past or future, to answer questions like how old someone was on their wedding day or how old they will be when a policy starts. Your date of birth never leaves the browser.
How exact age is counted
The calculator counts whole months from the birth date first and then the remaining days. If the birthday falls on a day that a shorter month does not have, it uses that month's last day. Someone born on 31 January is therefore one month old on 28 February (or 29 February in a leap year), not on 3 March. Years are simply whole months divided by twelve.
Leap-day birthdays follow the same rule. A person born on 29 February has their birthday counted on 28 February in common years and on 29 February in leap years. Born on 29 February 2000, they turned exactly 1 year, 0 months and 0 days old on 28 February 2001, and on that day the next-birthday panel says it is the birthday. Laws differ on this point: some places treat 1 March as the legal birthday in common years, so check local rules when the exact day has legal weight.
The totals are counted from the calendar dates. Total days is the number of days between the two dates, total weeks is that number divided by seven and rounded down, and total hours is days times 24. The time of birth is not used.
Reasons to calculate an exact age
Forms, eligibility and deadlines
School entry, sports age groups, visas, pensions and insurance often depend on age on a specific date rather than today. Put that date in Age at date and you get the age the rule cares about.
Milestones and celebrations
Turning 10,000 days old, a first-month celebration for a baby or counting how many weeks until a big birthday are easy to check once the totals are in front of you.
Genealogy and history
Family historians often need the age of an ancestor at a marriage, census or death. Enter both dates and the years, months and days come out directly, without counting on your fingers.
A worked example
Take a birth date of 15 August 1990 and an Age at date of 15 October 2026. The calculator shows 36 years, 2 months, 0 days. The totals read 434 months, 1,887 weeks, 13,210 days and 317,040 hours. It also reports that 15 August 1990 was a Wednesday.
For the leap-day case, take 29 February 2000 measured on 15 October 2026. The result is 26 years, 7 months, 16 days, because the last full month ended on 29 September. The next birthday panel shows 136 days to go, turning 27 on Sunday 28 February 2027, since 2027 is not a leap year. In 2028 the birthday falls on 29 February again.
All of this runs as plain date arithmetic in your browser, independent of time zones. Today is taken from your device's clock, so if your device date is wrong the default will be too.
Cómo usar esta herramienta
- Enter the date of birth in the Date of birth field.
- Leave Age at date on today, or change it to any other date you want the age for.
- Read Your age in years, months and days, with total months, weeks, days and hours below it.
- Check the Next birthday panel for the countdown and the Day of the week born panel for your birth weekday.
Limitations
- Ages are counted in whole days. Hours are days times 24, not the exact hours since a time of birth, and daylight saving changes are ignored.
- If Age at date is earlier than the date of birth, no age is shown and a message asks for a later date.
- Dates use the Gregorian calendar. For a birth date recorded in the Hijri calendar, convert it first with the Hijri date converter.
- Leap-day birthdays are always counted on 28 February in common years, which may differ from the legal convention where you live.