/ˈtsaɪtⳀɡeɪbər/ · German for "time-giver"
In chronobiology, a zeitgeber is an external cue that resets your internal clock to the world around you. Light, temperature, food. That is exactly what the app does: it gives you the right cue, at the right time, so your body can adapt to the schedule you actually work.
Zeitgeber looks at your actual shifts and tells you exactly when to sleep, when to nap, when to stop drinking coffee, and when to get outside into daylight. A different plan for every day. All of it backed by 28 peer-reviewed papers.
"Keep a consistent bedtime." Great. Tell that to someone whose rota flips from days to nights every four days. You know the feeling. Not just tired. The thick, heavy, can't-read-a-sentence-twice kind of tired that follows you home at 8am and turns your days off into damage control.
You're not bad at sleeping. You just don't have a plan that accounts for the fact that you worked until 3am last night and you're back on at 7am tomorrow. Nurse, police officer, paramedic, factory worker. It doesn't matter. The standard advice doesn't apply to you.
No sleep hygiene tips. No "try chamomile tea." Zeitgeber generates a specific timeline for each day based on what shifts you're actually working, what your body clock naturally does, and where you are in your rotation.
Pick from common patterns (4-on-4-off, 7-day rotating, 2-2-3) or build your own. Takes about 90 seconds.
The algorithm reads your shift sequence and your chronotype, then builds a day-by-day plan. Sleep windows. Caffeine cutoffs. Nap timing. Light exposure. All of it specific to that day.
Check the app when you wake up. Your plan's there. It updates automatically when your rota changes. Nothing to think about.
The morning after a night shift and the evening before an early start are entirely different problems. Every day gets its own plan, shaped by your shifts, your chronotype, and what comes next in your rotation.
Caffeine has a half-life of roughly five hours. The app works backwards from your next sleep window and gives you a precise cutoff. Some days that is 2pm. Some days it is midnight. It depends entirely on your shift.
Light is the most powerful signal your body clock receives. Timed correctly, it shifts your rhythm by hours. Timed badly after a night shift, it undoes your recovery. Zeitgeber tells you when to seek it and when to block it.
A well-timed 20-minute nap before a night shift sustains alertness for hours. A 90-minute one completes a full sleep cycle. Get the timing wrong and you wake up groggier than before. The app handles both.
Gentle reminders for caffeine cutoff, nap window, wind-down. Delivered to your iPhone so you never miss a cue.
Your next recommendation on your wrist. Glanceable, no phone needed.
One tap sends your sleep schedule to whoever you live with. They see when you will be sleeping and when you will be up. No app needed on their end.
Coming off a block of nights is brutal. Without a plan, your days off disappear into a fog. Zeitgeber gives you a structured day-by-day recovery sequence so you actually reclaim your time off.
We find the best time to exercise based on your shifts and circadian rhythm. Body temperature peaks 6-8 hours after waking. We work around your rota to find a window that fits.
Every recommendation in Zeitgeber comes from a specific published study in sleep medicine or circadian biology. The caffeine cutoffs come from Drake et al. 2013. The light exposure timing comes from Czeisler's work on circadian phase-shifting. This isn't an app that bolted on a few references afterwards. The citations are the algorithm.
Tap any recommendation in the app and you'll see exactly which paper it's from, with a link to PubMed.
Read the full science page9 modules built into the app. Each lesson is a 4-5 minute read that explains the science behind your plan in plain English. Not dumbed down. Just clear.
How sleep cycles work, why shift workers get fewer of them, and what you can actually do about it.
The single biggest lever you have for moving your body clock. When to get it, when to block it, and why it matters more than melatonin.
Half-life, adenosine receptors, and why the coffee you had at 4pm is still in your system at 9pm. Your afternoon cup might be costing you 2 hours of sleep.
Your 3am commute home is statistically one of the most dangerous things you do. Meal timing, hydration, and staying alert when your biology is fighting you.
MBBS (MD-equivalent), Imperial College London
I studied medicine at Imperial College London. After qualifying, I spent two and a half years at BCG, working with healthcare companies and PE firms.
Having so many friends and family who work shifts, I saw first-hand what broken sleep does to people I care about. Shift work shaped my life long before I understood the science behind it.
The science exists. 28+ peer-reviewed papers spell out exactly what works. But nobody was putting it in people's hands. So I built it. Every recommendation in Zeitgeber traces back to a published paper. No vague advice. No guesswork.
28 days free. That's long enough to get through a full rotation and see if it's working. No card needed.
Coming soon. 28 days free, then £3.99/month. Cancel anytime.
Coming soon. 28 days free, then £34.99/year. Cancel anytime.
Zeitgeber runs entirely offline. No cloud. No analytics. No ads. No tracking. Your shift schedule and sleep data never leave your device. There's no server to hack because there is no server.
Coming soon. Drop your email to be first in line.
iOS only. Requires iOS 17 or later. Works offline.