How the countdown is computed
You supply an optional event name and a target date and time. The page stores the target as the browser's local time, converts it to a millisecond timestamp, and once a second compares it with Date.now(). The days figure counts whole calendar days from now using local date arithmetic; the leftover time is then split into hours, minutes and seconds. When the target moment is not in the future the display swaps to a "Time's up!" message that includes your event name. An empty target box shows a prompt instead.
The key design point is that the display is recalculated from the clock on each tick and not decremented. If the tab is hidden or the laptop sleeps, browsers may slow or pause the timer callback, but the first update after you return reads the real time, so the numbers jump to the correct value rather than drifting. The tab title is not changed, so you must keep the page visible to watch it.
Worked example
The default target is 1 January 2027 at 00:00. Seen at midnight on 1 December 2026, with no clock change in between, the display reads 31 days, 00 hours, 00 minutes, 00 seconds. Half an hour later it reads 30 days, 23 hours, 30 minutes and keeps ticking the seconds down.
Local time, time zones and DST
- The target is in your zone. A date typed here means local time for the device, so a viewer in another country would see a different instant for the same text. To plan across offices, first convert with the time zone converter, then enter the time in your own zone.
- Days are calendar days. A day is counted as the same clock time on the next date, not as 24 elapsed hours, so daylight saving changes do not leave the display an hour off. In New York, the countdown from midnight on 1 November 2026 to midnight on 2 November 2026 spans 25 real hours but shows 1 day and 00 hours, and the hours count then reflects the real time left after the whole days.
- "Days" are whole days only. Weeks and months are not broken out. For a calendar-aware difference between two dates, use date difference.
Other limits
- The target is not saved. Reloading the page restores the default event and date, so bookmark or note your own date.
- No sound or notification plays at zero, and nothing happens if the tab is closed. For repeating focus intervals, use the Pomodoro timer instead.
- To count years, months and days from a birth date rather than down to a deadline, the age calculator is the right tool.