Age Calculator

Age looks simple — subtract one year from another — but the honest version is subtler, because months are not the same length and years are not either. This calculator does the arithmetic the way a registrar or a court would: it counts whole calendar months and days, never a fake "30-day month," so the result is exact whether you were born in February or July, in a leap year or not.

The method walks forward from your birth date rather than subtracting digits. We add the largest whole number of years, then the largest whole number of months, that still does not overshoot today — and only then count the leftover days. When a month has to be clamped, it clamps to the real end of that month: one month after January 31 is February 28 (or 29 in a leap year), never a spill into March. Because every step uses the real length of each month, the answer self-corrects for 28-, 29-, 30- and 31-day months automatically and never lands on a nonsensical negative day count. The "How we calculate your age" panel shows this walk for your own dates, so nothing is hidden.

Totals — your age in months, weeks, days, hours, minutes and seconds — are counted from the exact instant of your birth to the current instant on your device clock, which means they already reflect your local time zone and any daylight-saving changes in between. Add your time of birth for true second-level precision; leave it out and we assume midnight at the start of your birth date, which stays exact to the day.

If you have ever checked your age on two sites and got answers a day or two apart, you were not imagining it. The disagreement comes from month lengths. Consider a span from January 31 to February 28. One reading says that is a whole month — end of one month to end of the next. Another says it is 28 days, one short of a full month because February has no 31st to land on. Both are legitimate; there is no single mathematically "correct" answer when the start day does not exist in the end month.

This tool uses the calendar-month convention: count as many whole months as genuinely fit, then measure the leftover days. That is the convention used on official forms, in medical records, and in law, which is why our years-months-days figure matches the age on your documents. The important part is that we are consistent and we show the rule we used — the failure mode to avoid is a calculator that silently approximates every month as 30 days and quietly drifts a few days off over a lifetime.

About one person in every 1,461 is born on February 29, and their birthday only appears on the calendar once every four years. That is a running joke — "I'm only ten, I've had ten real birthdays" — but it raises a real question for an age calculator: on what day does a leap-day baby get older in a common year?

The widespread legal answer is March 1: you complete a full year at the end of February 28, so you are considered a year older from March 1. Some countries and record systems instead roll the birthday back to February 28. Neither is universal, so rather than pick for you, this calculator detects a February 29 birth date and shows a toggle — choose March 1 or February 28, and your next-birthday countdown, your milestone dates, and your day counts all follow that choice. It also tells you how many actual February 29 birthdays you have celebrated.