Age Calculator

On your 25th birthday. Under the standard Western convention, you complete 25 full years at the start of that day — typically treated as midnight (12:00 AM) — so you are 25 throughout the entire day, not only after the hour you were born. The day before, you are still 24. This calculator follows that rule: it adds a year the moment the birthday date arrives. The distinction matters for age-gated activities, since legal age usually attaches to the start of the birthday rather than the exact time of birth. So if a license or benefit requires being 25, your birthday itself is the first qualifying day.

It counts a full year on February 28 in non-leap years. Because February 29 exists only every four years (and not in century years unless divisible by 400, so 1900 had none but 2000 did), a leap-day baby has no exact birthday in three out of four years. This calculator applies the common convention that the birthday effectively falls on February 28 in those years, so age increments on the 28th. Legal practice varies: many jurisdictions also treat February 28 as the birthday for age purposes, while some use March 1. For everyday counting the choice shifts the result by a single day, and only in non-leap years.

Because a month is not a fixed number of days. The years/months/days breakdown counts calendar months, which range from 28 to 31 days, while the total-days figure counts every individual day you have lived. Converting between them is not a clean multiplication: "3 months" might be 89, 90, 91, or 92 days depending on which months are spanned. The breakdown is computed by stepping forward whole years, then whole months from your last birthday, then the leftover days against the actual length of the preceding month. Both numbers are correct — they simply answer different questions, one in calendar units and one in raw days.

Yes, with one caveat for very old dates. The calculator uses the Gregorian calendar exclusively, which most of the world adopted in 1582, but different countries switched at different times — Britain and its colonies in 1752, Russia not until 1918. For any date before a region's adoption, the recorded "old style" Julian date can differ from the Gregorian date by several days, so an age computed from historical records may be off by that amount. For all modern dates the result is exact. If you are working with a pre-1752 birth date from old documents, check whether it was recorded in the Julian calendar before relying on a day-level figure.

Accurate to the second from an assumed midnight start. The seconds count treats your birth moment as 00:00:00 on your birth date, because birth time is not entered. If you know your actual time of birth, the true figure is offset by however many hours and minutes after midnight you were born. The calculation does correctly account for leap days within the elapsed span. It does not subtract leap seconds — 27 have been inserted into official time since 1972 to keep clocks aligned with Earth's rotation — but at under half a minute total across decades they are negligible for any everyday purpose. For legal or medical needs, years and days are what matter, not seconds.