Calendar math, explained.

Every day counts, including Saturdays, Sundays and public holidays. Adding 1 day moves to the following date; adding 0 days keeps your start date.

Years and months are applied together, then weeks and days. When a day does not exist in the destination month, it moves to that month’s last valid day.

The default excludes the starting date and includes the destination date. Counting both dates adds one to the absolute span. Reversing the dates gives a negative result.

Choose the timezone of the place where you were born. It identifies your birth instant and supplies the calendar for years, months, weeks and days. It initially uses the site timezone, but remains independent after the calculator opens. Travelling or changing your current location does not change your age. There is no separate calculation timezone.

Saturday and Sunday are excluded. The start is excluded by default; the inclusive option counts both endpoints if they are working days. Holiday data is limited to the displayed coverage years.

The starting point is the moment Start is selected. The first timer defaults to the current date and time, including seconds, in the selected site timezone. Additional timers default to the next minute boundary with seconds set to 00, and the display waits for Start before updating. Once started, it shows the actual time left until that fixed target, including time spent in background tabs. Changing the target while a timer is active keeps it running and immediately applies the new date, time or timezone. Stop stops display updates without changing the target or pausing time. At the target, the button returns to Start and a target-reached banner slowly fades away. A target in the past shows zero remaining time. Each timer has its own event name, target, timezone and Start or Stop control. The plus button, labeled Add timer, creates another independent timer; the minus button removes a timer. The Share icon copies a link containing the event name, target and timezone. Display copies a link to a read-only timer page that starts immediately. Opening the timer editor normally waits for Start. The Countdown link in an Add result starts it automatically, targeting midnight at the beginning of that result date in the selected site timezone. The target timezone defaults to the main settings. Selecting another zone interprets the target date and time in that zone and leaves the main settings unchanged. Shared links restore their own zone. Timezone lists run from east to west by the displayed UTC offset, from the most positive to the most negative. Places sharing an offset are alphabetical by their displayed city name. The header and My Age lists use current offsets; Countdown uses the target instant and timezone conversion uses the entered instant. Daylight-saving changes can change the order. Years and months are counted together and clamp to the destination month’s last valid day. Weeks are seven calendar days in the selected timezone; hours, minutes and seconds are the remaining elapsed time. Daylight-saving changes can make a calendar day 23 or 25 hours. Repeated local times offer a choice of occurrence. Years, months, weeks, days, hours, minutes and seconds always remain visible in one line, including when their value is zero.

Holiday data source: Nager.Holidays · Last updated: 2026-10-12 · 2025–2027. Holiday names are supplied by the data source in English.