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The Longest Timer

The longest timer there is: 99 hours, 59 minutes, and 59 seconds, set and ready to start. People search for a 10,000-hour timer, a one-million-year timer, even a timer for 10²⁴ minutes — and this is the honest answer to all of them. A stopwatch counts real seconds on a six-digit clock, and 99:59:59 is the most that display can hold, so it is the longest countdown this or almost any timer will run.

Press start and it counts down from just over four days. It is a fun thing to leave running, and a real answer to “what’s the maximum timer I can set?” For the exact phrasing of that ceiling, see the [99:59:59 timer](/fun-timers/99-59-59); for a normal length, the [countdown timer](/countdown-timer).

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Frequently Asked Questions

How long is the longest timer?
99 hours, 59 minutes, and 59 seconds — a little over four days. That is the maximum a six-digit HH:MM:SS display can show, so it is the longest this timer will count.
Can I set a 10,000-hour or one-million-year timer?
No. Ten thousand hours is over a year, and a million years is beyond anything a clock can count toward — a timer tracks real elapsed seconds, and the display tops out at 99:59:59. This page is set to that true maximum instead of pretending to count to a number it never could.
What happens when it reaches zero?
The same as any timer here — a sound and a spoken alert play the moment it hits zero. You would need to leave the tab open for the full four-plus days for that to happen.