Age Calculator

Inputs

Date of birth

The date to calculate age from.

As-of date

The date to calculate the age on. Defaults to today if left blank.

Calendar

Gregorian, Hijri or Both. Gregorian counts age in Gregorian years, months and days. Hijri counts it in Hijri months from a calculated Umm al-Qura table (1318 to 1500 AH only). Both shows one Gregorian-basis age with the matching Hijri dates beside it.

Results

Age

Complete years, then remaining complete months, then remaining days.

Total days

Whole calendar days from the date of birth to the as-of date.

Total weeks

Complete 7-day weeks in the total days lived; a partial week is not rounded up.

Total months

Complete calendar months from the date of birth to the as-of date, as a single combined count (distinct from the years/months/days breakdown).

Total hours, minutes and seconds

Total days multiplied out (x24, x1,440, x86,400). These are elapsed-time units derived from the calendar-day difference only, not from a time of birth: the calculator only ever accepts a date, never a time, so these are not birth-time-precise.

Day of birth

The weekday the date of birth fell on, alongside the date of birth itself.

Next birthday

Date of the first birthday after the as-of date.

Days remaining

Days from the as-of date to the next birthday.

Turning age

The age reached on the next birthday.

Hijri equivalents (Both mode)

The Hijri date of the date of birth, the as-of date and the next birthday, shown beside the Gregorian dates when they fall between 30 April 1900 and 16 November 2077.

Formulas

Worked example

For a date of birth of 20 August 1990 (a Monday), as of 5 March 2025: the age is 34 years, 6 months and 13 days. Total days lived: 12,616. Total weeks: 1,802 complete weeks. Total months: 414. The next birthday after the as-of date is 20 August 2025, 168 days away, turning 35.

Assumptions

• Age is calculated as complete years, then complete months, then remaining days, from the date of birth to the as-of date.
• A 29 February birthday is treated as 28 February in non-leap years. This is Calclabb's own convention, not a claim about any country's or organisation's rule.
• When a month-anniversary day does not exist (for example, a birth date of 31 January reaching a 30-day month), the day is capped to that month's last day.
• The calculation uses calendar dates only: no time of day or time zone is considered. "Today" is the date on your own device.
• Total hours, minutes and seconds are derived by multiplying the exact total-days figure (x24, x1,440, x86,400). They are not calculated from a time of birth, since this calculator only accepts a date of birth, never a time.
• Gregorian dates are supported from 0000-01-01 through 9999-12-31. Hijri dates (Hijri and Both modes) are supported only from 1318 to 1500 AH.
• The date of birth must not be after the as-of date.
• Gregorian mode and Both mode calculate age on the Gregorian calendar. In Both mode the Hijri dates are calendar equivalents of the same days, from a calculated Umm al-Qura table (1318 to 1500 AH, 30 April 1900 to 16 November 2077), not a second age calculation. A day outside that range gets no Hijri equivalent: it is never estimated.
• Hijri mode counts age in Hijri months over the same table. Months have 29 or 30 days, and a 30th that falls in a 29-day month is counted on the last day of that month. The table is a calculated calendar, not moon-sighting, and has not been directly verified against the official KACST service, so it must not be used to decide the start of Ramadan, Eid or Hajj.

Common questions

What does this calculator do?

It works out how old someone is from a date of birth, given as complete years, months and days, and also shows total days, weeks, months, hours, minutes and seconds lived, the weekday of birth, the next birthday, and how many days are left until it.

How is age calculated?

Years and months are the largest whole calendar units from the date of birth to the as-of date; days are the remainder. A month "anniversary" is the same day-of-month, counted from the original date of birth.

How many days, weeks or months old am I?

Total days is every whole calendar day from the date of birth to the as-of date. Total weeks is the complete 7-day weeks within that (a partial week is not rounded up). Total months is the complete calendar months across the same span, as one combined count.

What day of the week was I born?

The calculator works this out deterministically from the date of birth (the Gregorian calendar repeats on a 7-day cycle) and shows it as "Day of birth" alongside the date itself.

What does the "as-of date" mean?

It is the date the age is calculated on. It defaults to today if left blank, but can be set to any other date to see the age on that day instead.

How are leap years and 29 February birthdays handled?

29 February is a valid date of birth in a leap year (such as 2024 or 2000). In a year that is not a leap year, a 29 February anniversary is treated as 28 February. For example, a date of birth of 29 February 2000 gives 24 years, 11 months and 29 days on 27 February 2025, and exactly 25 years on 28 February 2025. This is Calclabb's own convention, not a claim about any country's or organisation's rule.

What does "next birthday" mean, and what if the as-of date is my birthday?

The next birthday is the first birthday after the as-of date, shown with the days remaining and the age reached. If the as-of date is itself your birthday, the result says so and shows the age you turn that day, instead of counting on to the following year.

Which calendar does this use, and can I calculate Hijri age?

The Gregorian calendar by default, for dates from the year 0000 to 9999. Choose Hijri in the Calendar selector to count age in Hijri months, or Both to see the matching Hijri dates beside the Gregorian age. Hijri dates are supported from 1318 to 1500 AH (30 April 1900 to 16 November 2077) only, and dates outside that range are refused rather than estimated.

What happens when the month-anniversary day does not exist in the target month?

The day is capped to that month's last day. For example, a date of birth of 31 January reaching a 30-day month counts its anniversary on the 30th.

Are the total hours, minutes and seconds exact to the time I was born?

No. This calculator only accepts a date of birth, never a time, so total hours, minutes and seconds are calculated by multiplying the exact total-days figure (x24, x1,440, x86,400), not from an actual birth time.

What do the Gregorian, Hijri and Both modes do?

Gregorian calculates age on the Gregorian calendar. Hijri calculates it in Hijri months, for dates from 1318 to 1500 AH only. Both keeps one Gregorian-basis age and shows the Hijri equivalents of the same dates beside it.

Why does Hijri mode give a different age from Gregorian or Both mode?

Hijri months are shorter than Gregorian ones, so the same two dates give different years, months and days. The total number of days between them is the same in every mode.