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Date & Time

Age Calculator

Work out an exact age in years, months and days from a date of birth, plus total months, weeks and days and the countdown to the next birthday.

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Calculate age
Defaults to today. Change it to find your age on any other date.

How to use the age calculator

Enter a date of birth and press Calculate. The second box, Age at the date of, is filled with today's date from your device. Change it if you want to know how old someone was or will be on another day, such as a school start date or a retirement date.

The result shows:

  • The exact age in completed years, months and days.
  • The same span as total months, total weeks and total days.
  • The date of the next birthday, the age that will be reached on it and how many days are left.

How the age is worked out

The calculator counts how many full months have passed since the date of birth, then counts the remaining days. Twelve full months make one year. A month is complete when the same day number comes round again in a later month.

Worked example

Take a date of birth of May 15, 1990 and an "age at" date of October 16, 2026.

  • From May 15, 1990 to May 15, 2026 is 36 full years.
  • From May 15, 2026 to October 15, 2026 is 5 more full months.
  • From October 15 to October 16 is 1 day.

The age is therefore 36 years, 5 months and 1 day. Counted another way, that is 13,303 days, or 1,900 weeks and 3 days. The next birthday falls on May 15, 2027, when the person turns 37.

Good to know

  • Leap day birthdays. If you were born on February 29, the calculator treats February 28 as your birthday in years that are not leap years. On February 28, 2027 someone born on February 29, 2000 is counted as having turned 27. In leap years the birthday stays on February 29.
  • Month ends. When a birth day number does not exist in a shorter month, the last day of that month is used. Someone born on January 31 completes their first month on February 28 (or 29 in a leap year).
  • The day of birth is day zero. On the day you are born your age is 0 days, and on your first birthday it is exactly 1 year.
  • Time of day is ignored. Ages are counted in whole calendar days, so the hour of birth and time zones do not change the result.
  • The "age at" date cannot be earlier than the date of birth. Dates from year 1 to year 9999 are supported, using today's Gregorian calendar for all of them.

Frequently asked questions

How is my age calculated in years, months and days?

The calculator counts the full months between your date of birth and the chosen date, turns every 12 months into a year, and then adds the days left over since the last monthly anniversary of your birth date.

I was born on February 29. When is my birthday in other years?

In years without a February 29, this calculator uses February 28 as your birthday. That is the date on which your age goes up by one year in the results, and it is shown as your next birthday when the coming year is not a leap year.

Can I find out how old someone was on a past date?

Yes. Change the "Age at the date of" box to any date after the date of birth. The calculator then shows the age on that day, along with the total months, weeks and days up to it.

Why does the calculator use today's date from my device?

Today's date is read from your own device when the page loads, so the result matches your local calendar day wherever you are. If your device clock is wrong, simply type the correct date into the box.