Why do interval timers drift?

Because many of them run on an internal tick that fires once a second. A tick scheduled for one second actually fires a beat later, and that beat is never given back. After a few hundred intervals the session is running long, even though every screen still shows the number you set. Timers that take the remaining time straight from the system clock, the way a stopwatch does, don't collect that error.

Why does my timer stop when the screen turns off?

It's usually the phone managing background apps, not a crash. Android slows or sleeps apps it considers idle, and phone makers add their own battery layers on top, some of which kill background apps outright. iOS freezes an app at lock unless it plays audio in the background. Two settings are worth checking: battery-optimization exemption on Android, and screen auto-lock on iOS, which otherwise times out mid-set. If the timer dies only while other audio apps are running, that's a different failure, on the audio channel.

How do I test my interval timer for accuracy?

On day one, before the app has your workouts saved. For drift, program ten rounds of ten seconds on, ten off; the session should finish in 3:20 flat against the clock on your oven. For background, run one three-minute round with the phone locked in a pocket and see whether the bell lands on time. Seven minutes total, and you'll know whether to keep the app.

Does Intertakt keep running with the screen off?

Yes. The session carries on with the display dark: beeps on DND, a lock mode guarding against accidental taps. Long sessions hold their length, since the cues are timed against a monotonic clock. Answering a call stops the round, and the app remembers the exact moment to restart from. The Android build is [out on Google Play](https://play.google.com/store/apps/details?id=com.intertakt.intertakt&utm_source=intertakt-site&utm_medium=blog&utm_campaign=interval-timer-drift&utm_content=inline-en); iOS comes later, and the waitlist on this site mails you once when it does.

Can you trust your interval timer? Drift, background kills

You find out mid-set. The rest you set at thirty seconds takes closer to forty, or the phone you flipped face-down between rounds turns out to have killed the app two rounds ago. During burpees, checking the clock is the timer’s job, and the timer does it where you can’t see it. You set the numbers once; how work and rest build one session is the timer’s problem from there.

None of this is new. Thirty-four reviews spread across eight years and four timer apps, and one line covers them: “It stops running when the screen goes off, when you take a call.” A three-star review from this August, about an app that has been sold for a decade: “adding extra time to each interval and counts up.”

A timer that quietly runs slow

Most timers are designed around a tick. Every second, the app wakes up, adds one to a counter, and goes back to sleep. It sounds right, and it drifts, because every tick lands a little late. The phone was busy, or the operating system throttled the app for a moment; the delay folds into your interval and stays. Twenty rounds later, your 20/10 has quietly become 21/11.

An older fix exists: the timer asks the system what time it is and computes what’s left. The pauses of the phone stop mattering, because nothing accumulates. When an interval app is “adding extra time to each interval”, a tick counter is adding up every delay it was handed.

You can measure this in one throwaway session. Program ten rounds of ten seconds work, ten seconds rest, which is 3:20 end to end. Run it next to a kitchen timer with the screen on and no other apps running. If it finishes at 3:29, you’ve found drift in under four minutes.

A phone that kills the timer

The second failure happens outside the app. Both platforms treat a backgrounded app as a battery cost, and they act on that belief hard. Android puts idle apps to sleep and lets the vendor’s battery manager, which Samsung, Xiaomi and others ship on top, kill anything that has been in the background too long. iOS suspends an app the moment the screen locks unless the app holds a specific background arrangement.

You pick the phone up between rounds and the session is gone. The wish, from a runner who also tracks with Strava, comes as one line: “won’t crash when Strava and Spotify are running.” A timer that survives the lock screen but dies when a podcast app grabs the audio channel fails you at an especially bad moment, with your hands full and the phone out of reach.

The standard fixes tell you how bad the defaults are. On Android, the advice is to dig into settings and exempt the timer from battery optimization by hand. On iOS, one kettlebell lifter wrote in March that he “couldn’t find a way to stop my screen (on iOS) from turning off mid set without manually stopping in the iOS settings.” The user’s job, apparently, is to reconfigure the phone so the timer can keep working.

A timer made for interval work takes that fight on itself: running with the screen off, in your pocket, on DND is the promise, and underneath it the audio keeps playing from the background with the screen locked, and the next cue is scheduled to fire even if the app is resting when the moment comes.

The seven-minute check

Do these two before the app earns your presets. Once the timer has your rounds saved, switching costs more than the tests do.

The drift test is the 10 × 10/10 session from above, timed against the same kitchen timer. The pocket test: program a three-minute round, press start, lock the phone, put it in your pocket, and walk away. Come back when the bell should have rung. If the count matches the wall clock and the cues fired while the screen was dark, the timer passed; a session parked at 2:14 waiting for a screen tap failed.

If both pass, you can stop thinking about the timer during workouts.

What a timer owes you

Reliability comes down to four statements an app should be able to make plainly.

It keeps the intervals you set, and a long session does not run longer than the math. It keeps going when the screen goes dark. It runs alongside other apps: music, a podcast, a run tracker, whatever sits in front. And when something interrupts it, a call for instance, it tells you where it stopped and resumes from there.

Apps that cannot make those four statements usually make vaguer ones, like “optimized timing” where “runs with the screen locked” would have been more useful.

Where Intertakt stands

Both failure modes above were the brief for Intertakt. The phone goes in face-down with the screen locked and DND on; audio keeps running, and a lock mode keeps stray touches from pausing anything. Timing comes off a monotonic clock, so thirty minutes of intervals finishes at thirty minutes, and intervals are set in whole seconds, 15-second steps included. A call pauses the round; the app names the moment it stopped and picks the round back up when you return.

Intertakt is out on Google Play. Run the seven-minute check before you hand it your rounds; it is two of the six in telling a solid timer from a weekend clone. If you want one email when the iOS version lands, leave your address on the waitlist here.