Age Calculator

How do you calculate age in years, months and days?

Enter your birth date and a reference date to calculate complete calendar years, months and remaining days. For example, January 31, 2000 to March 1, 2000 gives 0 years, 1 month and 1 day. The calculator first tries two months, reaching March 31. That is after the reference date, so it uses one month instead: February 29. One remaining day reaches March 1.

This is why subtracting years or dividing days by 365 does not reproduce the result. The calculation adds months from the original birth date, clamps a day that does not exist to the target month's last day, then splits complete months into years and months. Open How it's calculated to see those anchors for your own dates.

Calendar age examples with dates only

Birth date	Reference date	Calendar age
January 31, 2000	February 29, 2000	0 years, 1 month, 0 days
January 31, 2000	March 1, 2000	0 years, 1 month, 1 day
January 1, 2000	April 1, 2026	26 years, 3 months, 0 days

How do you find age on a past or future date?

Calculate age as of starts with today's local date. Change it to check age at an anniversary, application date or planned event. The birth-date field is capped at today, while the reference date can be in the future. A reference date before birth produces no age result. Using the birth date itself gives zero elapsed days.

The calculation does not choose legal eligibility rules for you. Its month-end convention describes the arithmetic used here; a form or authority may require a different convention. For a general interval between two dates, use the Date Difference Calculator. Other tools are available in the calculators collection.

How many weeks, hours and minutes old are you?

Open Totals and milestones for the expanded totals. From January 1, 2000 to 2026-01-01, the calculator returns 9,497 calendar days, 1,356 whole weeks, 227,928 hours and 13,675,680 minutes. Total months is 312. Weeks discard the remainder after division by seven; total months counts completed calendar months rather than dividing days by an average month length.

The regular hours and minutes totals multiply calendar days by 24 and 1,440. They do not include a birth time or account for shorter or longer days caused by clock changes. Calendar days use UTC arithmetic on the selected date components, avoiding an extra or missing day from ordinary daylight saving transitions. Use the optional precision section for elapsed time between specified clock times.

What changes when you enter a birth time and time zone?

Open Birth time and time zone (optional), enter Birth time and Reference time, then check Time zone for both dates. The zone initially follows your browser. One zone applies to both inputs; there are no separate birth and reference zones. These inputs produce elapsed minutes, whole hours with remaining minutes, and minutes until the next birthday at the birth time.

This result leaves the main calendar age unchanged. Repeated clock times resolve to their earlier occurrence. An entered time inside a clock-forward gap produces an error instead of an invented instant. When a future birthday falls in such a gap, its time moves forward by the gap. A reference instant before the birth instant also produces an error, even when the two calendar dates match.

How does the leap-day birthday option work?

Under Age options and compare people, the Leap-day birthday (Feb 29) selector defaults to Next Feb 29. For February 29 births, it can instead use Feb 28 in common years or Mar 1 in common years. The choice controls the next birthday date, its day countdown, and the optional time-based countdown.

It does not change the years, months and days calculation. That calculation still clamps month anchors to month end. On the selected birthday date the date-only countdown reads Today!; the precision countdown also checks the birth time. Gregorian century rules matter: 2100 is not a leap year, so actual February 29 birthdays can be eight years apart.

When do you reach birthday and lifetime milestones?

The milestone list adds 10,000, 15,000 and 20,000 calendar days to birth, counting birth as day zero. Someone born on January 1, 2000 reaches the 10,000th day on Wednesday, May 19, 2027. Each entry shows its weekday and whether it has been reached relative to the reference date. Dates beyond year 9999 are omitted.

The billionth-second milestone adds exactly 1,000,000,000 seconds to birth assumed at local midnight and displays the local time. It does not use your optional birth-time input. Add to calendar downloads a one-day, all-day .ics event, including for that timed milestone. Import it yourself; it does not create a timed alert or recurring birthday series. Copy result copies calendar age plus total days and whole weeks.

What are Korean and Chinese traditional age?

Age system offers International, Korean (year count), and Chinese traditional. Korean age uses reference year minus birth year plus one: it starts at one and increases at January 1. For someone born December 31, 2000, 2026-01-01 gives Korean age 27 alongside international age 25.

Chinese traditional age starts at one and increases at Lunar New Year. The tool uses the browser's built-in Chinese calendar to find that boundary. When the calendar is unavailable, it displays an unsupported-calendar message. These options add a comparison value; the main result remains international calendar age. They do not provide a legal age determination.

How do you compare several people's ages?

Compare people begins with two rows. Use Add person for up to five, or Remove to delete a row. Each person uses the shared reference date and selected age system. Names are optional; blank names display as Person 1, Person 2, and so on.

The age gap compares only the first two birth dates, from the earlier to the later, using the same calendar-month method. It does not compare every pair or use birth times. Changing the reference date changes each person's age but not the interval between their birth dates.

What does the birth weekday mean, and where do your dates go?

Born on uses JavaScript's Gregorian calendar weekday. It does not convert historical Julian-calendar records, so confirm the calendar behind an older recorded date before entering it. The parser rejects nonexistent dates rather than silently accepting February 30 as a March date.

Birth dates, names and options stay in React page state; the calculator does not upload them or write them to cookies or localStorage. Reloading resets the inputs. No camera, contacts or location permission is needed. Copying a summary or downloading a calendar is an explicit action; keep the resulting clipboard text or file private if it contains personal information.