Nadir

Caffeine timing for people whose schedule doesn’t care what time their body thinks it is.

Not yet on the App Store

Most caffeine apps are counters. You tell one that you drank a coffee, it adds 95 to a running total, and nothing about that number changes what you do next.

Nadir predicts instead. It models how alert you will be over the next two days — the sleep pressure building since you woke, the body clock that makes 4am worse than 2am, and the caffeine still in your blood — then works out when to drink so you are sharp when it matters and can still sleep afterwards.

Support

Questions, bugs and feature requests all go to the same place:

Common questions

I paid, but Pro is not showing up

Open You → Restore purchases, or tap Restore purchases at the bottom of the Pro screen. Your purchase is tied to your Apple Account, not to this phone, so it will come back on a new device or after reinstalling — make sure you are signed in with the same Apple Account you bought it on.

Why not just tell me a caffeine cutoff time?

Because a fixed hour is wrong in both directions. It forbids a harmless 9am espresso and permits a 3pm cold brew that is still working at midnight. What actually matters is how much caffeine is left in your blood at bedtime, and that depends on the dose, the timing and your own metabolism. Caffeine half-life varies more than twofold between healthy adults.

What half-life should I use?

Five hours is the population average and a reasonable starting point. Nudge it up if caffeine keeps you awake more than it seems to for other people, or down if a late coffee never troubles you. Oral contraceptives roughly double it; heavy smoking roughly halves it. It is the single setting that changes the advice most, which is why it is the first one on the screen.

It says no dose helps. Is that a bug?

No. It means nothing within your own limits — your daily ceiling, your per-dose ceiling, and the amount you are willing to still have on board at bedtime — would reach the target you asked for. The app says so rather than recommending a bigger dose to look useful. Sometimes the answer is sleep.

Where is my data, and how do I delete it?

On your phone, in a single file inside the app, and nowhere else. There is no account and no server. Deleting the app deletes the data with it.

Does it need HealthKit or my location?

Neither. Nadir asks for no permissions at all.