3weeks
Build habits in 21 days — the science-backed habit tracker
Related Posts15
Why 3weeks Was Built — The Pattern Behind Resolution Failures
Resolutions fail repeatedly for predictable reasons: goals are too vague, timeframes too long. 3weeks addresses this with a concrete 21-day unit.
3weeks Streak Structure — How Consecutive Records Create Motivation
3weeks resets to zero if you miss a day. This strict structure is exactly what motivates daily execution.
Habits That Work Well with 3weeks
3weeks is built around a daily consecutive check structure. Habits that are doable every day with clear completion criteria are the best fit.
3weeks — Why 21 Consecutive Days?
3weeks locks the goal period to 21 days. Here's the habit formation theory behind that choice.
3weeks Dev Log #10 — Finally: iOS and Android Simultaneously
An app that started as iOS-only in 2019 launched on Android in 2026. Flutter made it possible.
3weeks Dev Log #9 — Making It a Game: Badges and Statistics
I wanted to move past a plain check-off app. Collecting badges, seeing your progress in stats, watching habits accumulate visibly — that was the goal.
3weeks Dev Log #8 — From UIKit to Flutter: What the Tech Stack Switch Actually Looks Like
Swift UIKit + Realm to Flutter + Hive. Rebuilding the same features in a different language and framework was more interesting than I expected.
3weeks Dev Log #7 — Four Years Later, Rebuilding in Flutter
Decided to replace the Swift UIKit app entirely with Flutter. The technical reasons were secondary — I wanted to make the app genuinely more fun.
3weeks Dev Log #6 — After 1.1.3, Four Years of Silence
May 2, 2023, 6:26 AM — version 1.1.3 shipped. That was it. Nearly four years went by without touching the app.
3weeks Dev Log #5 — Saying It Out Loud Helps: Voice Memo Feature
Research suggests that vocalizing something helps encode it. So I added a voice recording feature — record a message, hear it every time you check in.
3weeks Dev Log #4 — Without a Reward, Habits Don't Stick
I learned that habit formation requires a reward system. The app can't give rewards directly. But it can let users define their own — and that turned out to matter.
3weeks Dev Log #3 — July 25, 2019, 4:58 AM: First Launch
4:58 in the morning. The App Store approval email arrived. That's what it feels like when your app enters the world.
3weeks Dev Log #2 — The 21-Day Rule: Consecutive, Reset, Complete
The app had one core rule: 21 consecutive days. Miss one day and you're back to zero. Simple as it sounds, how you implement that rule is what the whole app is built on.
3weeks Dev Log #1 — How a Single Talk Became an App
In 2019, I watched a talk and decided to build an app. I didn't expect 'just keep doing it for 21 days' to stay in my head this long.
3weeks — Building the Hypothesis That 21 Days Is Enough
Habit apps are everywhere. Most of them fail. Here's why the 21-day challenge concept works — and what building it as an app taught me.