Constraint-based scheduling
Find the calm hour in your week.
Your calendar isn't full — it's tight. Slack Tide knows your sleep, your work hours and the time you keep for yourself. When you want to do something, it doesn't ask you when. It tells you.
Beta for iOS. Android is next.
The problem
Calendars show you gaps, not availability.
Tuesday 22:30 looks free on your calendar. But if you sleep at midnight, that gap isn't real. And if you already did three things that day, a technically empty hour won't rest you — it will drain you.
A gap is not availability
An hour that survives sleep, work and travel time is the only kind that counts.
Density is invisible
Five back-to-back events are five boxes on a calendar and one exhausting day in a body.
Shared time is hard
Finding an hour that suits two people isn't solved by putting two calendars side by side.
How it works
You say three things. The engine works out the rest.
- 01
Set your constraints once
When you sleep, when you work, how much time you want for yourself each day. Setup takes three steps.
- 02
Say what you want to do
No need to pick a time. Tell it how long it takes, how urgent it is and the window it could happen in.
- 03
Get an option with reasons
The engine ranks the three best times and writes down why it chose each one. If you disagree, you can see what it weighed.
Example
"Shall we go go-karting this week?"
A friend messages you. You add them in the app and create a shared event. Once they accept, the engine intersects both sets of constraints — sleep, work and downtime.
The reasoning stays: you can always see why this hour was chosen.
Saturday, August 15
score 9109:00 – 11:00
Saturday 09:00 — your calmest day in this window — 73% breathing room, you're usually more energetic at this hour, it suits both of you about equally.
The engine
What decides isn't a guess.
Slack Tide does two things in order: it rules out everything impossible, then scores what remains. A slot that lands in your sleep, your work hours or an existing commitment is never produced — not filtered out afterwards, never produced.
- Breathing room 30%
- How much free time that day leaves you
- Energy fit 20%
- Whether you are a morning or evening person
- Preference fit 20%
- The days and hours you asked for
- Urgency 15%
- How close the deadline is
- Context 10%
- Whether nearby plans are of the same kind
- Fairness 5%
- How evenly a shared event suits both sides
The same input always produces the same result. The engine uses no randomness.
Routines
Working out three days a week does not mean three days in a row.
For recurring things you say how many times a week; the engine decides which days and spreads the repeats apart. If the week is full it tells you how many fit and what stopped the rest.
Your data
Your calendar is yours.
Slack Tide has to know your sleep and work hours to work at all — that is personal data and it is treated as such. We do not sell it, we do not use it for advertising, and deleting your account deletes your scheduling data with it.
Privacy policy →Questions
Frequently asked
Do I have to connect my calendar?
No. Slack Tide works from your own constraint profile: sleep, work and downtime. Calendar sync is a convenience we may add later, not a requirement.
What if I don't like the suggested time?
Every suggestion comes with its reasoning, so you can see why that hour. Three options are offered; if none work, the engine tells you what blocked the rest and what you could change.
Does my friend need the app too?
For a shared event, yes. An hour that suits both of you cannot be worked out without both sets of constraints.
Is my downtime protected?
Yes. Your daily downtime is closed to scheduling. Only items you mark as critical can cross that line, and the app says so explicitly when they do.
When is Android coming?
The app is written in React Native, so an Android build is technically ready. It is next in the beta queue after iOS.
Join the beta.
Slack Tide is in closed testing on iOS. You can try it through TestFlight and send feedback directly.
Try via TestFlightBeta software; expect gaps and changes.