12 Hour Timer

A 12 hour online countdown timer for half-day intervals, long fasts, overnight shifts, and 12-hour deadlines. Notifies you exactly 12 hours later.

Countdown timer

Quick utility for focus sprints or breaks — runs in the browser.

Channels
Browser (off)
Remaining
--:--
Twelve hours is the length of an overnight shift, the 12:12 intermittent-fasting interval, a long-haul flight, the standard pickling window for many recipes, and a half-day deadline. Once the duration crosses many hours, the timer must run server-side — relying on a tab to stay open, a phone to stay unlocked, or a watch to stay synced is asking for failure. This page sets a 12-hour timer that runs entirely on the server, so the countdown survives device restarts, tab closes, screen locks, and switches between devices. Press start, label the block ("overnight shift", "fast end", "pickle", "deadline"), pick a notification channel — Telegram, browser push, or email — and the alert reaches you exactly 12 hours later. For an intermittent-fasting routine, save as a daily recurring reminder so the fast window opens and closes automatically at the same time every day. For shorter intervals, the 8-hour timer covers a workday or sleep cycle; for longer, the 24-hour timer is one click away. Twelve hours is also the natural unit for flipping between half-day modes in a polyphasic schedule.

FAQ

Is the 12-hour timer good for intermittent fasting?
Yes. The 12:12 method has both a 12-hour eating window and a 12-hour fasting window. Save the timer as a daily recurring reminder so each transition fires automatically.
Will the 12-hour timer survive a laptop restart?
Yes. The countdown is scheduled entirely on the server, so no client-side state — tab, browser, device, or network — matters until the notification fires.
Can I use it as an overnight-shift timer?
Yes — start at the beginning of the shift, label "overnight shift", and the end notification arrives via Telegram, push, or email exactly 12 hours later.
Can I make 12 hours recurring?
Yes. After one run, save it as a daily reminder so the timer is queued automatically every day at the same time.

Related timers

← RemindMeNow