Age Calculator

Frequently asked questions

How do I calculate my age from my date of birth?

Enter the date of birth and the calculator counts the completed years, then the completed months on top of those, then the days left over — which is exactly how age is counted in conversation and on a form. Born on 20 May 1990, on 16 September 2026 you are 36 years, 3 months and 27 days old: 36 years takes you to 20 May 2026, three more months to 20 August, and 20 August to 16 September is 27 days. The same age is also shown in whole months, weeks, days and hours, because a form asking for a baby's age in months or a visa form asking for age in days wants the figure counted differently.

Why does dividing the days by 365 give a different answer?

Because a year is not 365 days and a month is not 30. Dividing by 365 loses a day for every leap year in the span — about nine days over 36 years — and dividing the remainder by 30 then spreads the error across the months, so the answer drifts by a day or more and changes depending on which months the span happens to cover. This calculator never divides: it works out how many actual calendar anniversaries have passed, so 29 February, the 28-day February and the century rule that made 1900 an ordinary year are all handled by the calendar rather than by an average.

How many days are there between two dates?

Use the Days between tab. It gives two figures because contracts mean different things by the same phrase: the gap between the dates, and the count that includes both the first and the last day — which is how leave, notice periods and hotel stays are normally written, and is always one more. It also splits the span into weekdays and weekend days, so a deadline quoted in working days can be checked at a glance. Public holidays are not deducted, since those differ by country and state.

What age is someone born on 29 February?

They have a birthday every year; in three years out of four it is the date itself that goes missing. In a common year this calculator treats 28 February as the birthday, so someone born on 29 February 2000 turns 23 on 28 February 2023. That matches the rule in England and Wales and in India, where a person born on the 29th attains an age at the start of the last day of the corresponding month. Hong Kong and several US states take 1 March instead, so the tool names that date too rather than pretending the question has one answer.

What happens when the month is too short for the date?

One month after 31 January has no arithmetic answer — only a convention. This tool, like every mainstream date library, moves to the last day of the shorter month, so 31 January plus one month is 28 February (29 in a leap year), and it says so on screen when that rule has been applied instead of leaving you to wonder. One consequence is worth knowing: adding a month twice is not the same as adding two months, because the first step loses the 31st. 31 January plus one month twice is 28 March; plus two months is 31 March.

Does the answer change with my time zone?

No. The calculator works in whole calendar dates and never converts to UTC, which is the bug behind date tools that show yesterday's answer to anyone west of Greenwich — a date string read as UTC midnight becomes the previous evening in New York. Days, months and years here are counted with exact integer arithmetic on the calendar itself, so the result is the same wherever you are and is unaffected by daylight saving. Nothing you enter leaves your device.