Birthday Countdown Calculator

Enter a name and a birth date. The calculator finds the next time that month and day come around (this year if the birthday has not happened yet, otherwise next year), then subtracts the current moment from it. The difference is split into days, hours, minutes and seconds and refreshes every second while the page is open.

1. Your age is this year minus your birth year, minus 1 if your birthday has not happened yet this year.
2. The next birthday is your birth month, day and time placed in this year or the next.
3. Time left = next birthday minus now, shown as days, hours, minutes and seconds.
4. Days lived = now minus your birth date and time, divided by one day (86,400 seconds).

Example: on 1 January 2026, a birthday on 14 June is 164 days away (31 + 28 + 31 + 30 + 31 = 151 days to reach 1 June, plus 13 more). The gap between two birthdays is 365 days, or 366 when a 29 February falls in between: 15 June 2026 to 15 June 2027 is 365 days, while 15 June 2027 to 15 June 2028 is 366.

The countdown reaches zero at the birth time you enter (12:00 by default), not at midnight. Change the birth time to 00:00 if you want the countdown to end when the date changes.

A 29 February birthday only exists in leap years, which come every 4 years (1,461 days apart, because 4 x 365 + 1 = 1,461). Someone born on 29 February 2000 has had only 6 real birthdays on the 29th by 2024: in 2004, 2008, 2012, 2016, 2020 and 2024.

In years without a 29 February, this calculator moves the birthday to 1 March. Many people celebrate on 28 February instead, and the legal age rules differ between countries, so use the countdown for planning and check official rules for anything formal. Century years such as 2100 are not leap years, so a leapling will wait 8 years between 29 February birthdays at that point.

The countdown uses your device clock, so it follows the time zone your device is set to. A birthday is a calendar date, so it arrives earlier for people further east: someone in Auckland (UTC+12 in winter) sees a date change about 12 hours before someone in UTC. If you travel, the number of days left stays the same, but the exact hour the countdown ends moves with your clock.

• 10,000 days old: someone born on 1 January 2000 reaches this on 19 May 2027 (about 27.4 years).
• A year is 365 days, so 30 years is 10,950 days plus leap days. From 1 January 2000 to 1 January 2030 it is 10,958 days, because 8 leap days fall in between.
• Age and days lived are different things: age counts completed birthdays, days lived counts every day since birth.