I'm not going to tell you if 4-day weeks work.
I'm going to show you my git log for the last 90 days. You decide.
Context: I write C++ search engines. Solo. No meetings. No manager. Just me and a codebase called glyph-engine.
For 3 months, I worked Mon-Thu. Fri-Sun I wrote zero code. No laptop. No "quick fixes".
Here's what happened to my output, my bugs, and my brain.
The Data: My GitHub Doesn't Lie
First, proof I'm not making this up. This is my May 2026: 363 commits across 6 repos.
Notice the pattern? Heavy Mon-Thu. Dead Fri-Sun. That's intentional.
187 of those commits went to glyph-engine, a disk-based FM-index I built:
The repo got traction too. 1,043 clones and 414 unique cloners in 14 days:
Now, the actual experiment. I compared 3 months of 5-day weeks vs 3 months of 4-day weeks on the same codebase.
Results:
| Metric | 5-Day Weeks | 4-Day Weeks | Change |
|---|---|---|---|
| Commits / Week | 22 | 14 | -36% |
| Lines Added / Week | 1,240 | 780 | -37% |
| Lines Deleted / Week | 410 | 1,190 | +190% |
| Bugs per 1k LOC | 4.2 | 1.7 | -59% |
| Days to Merge Feature | 9.2 | 4.8 | -48% |
Translation: I wrote 37% less code. But I deleted 190% more garbage. Net result: features shipped 2x faster with 2.5x fewer bugs.
Why It Worked: The 3-Day Defrag
My brain has cache. Just like a CPU.
Day 1 off: L1 cache flush. I'm still thinking about yesterday's segfault. Useless.
Day 2 off: L2 cache flush. I start forgetting variable names. Good.
Day 3 off: L3 cache flush. This is where magic happens. I wake up and realize my suffix array layout thrashes the TLB. The fix is obvious.
With 2-day weekends, I never hit Day 3. I was stuck debugging symptoms. With 3 days, I fixed root causes before I wrote them.
My CPU does 37 GB/s. My brain does ~37 thoughts/s. Both need idle cycles to defrag. 2 days isn't enough.
When This Fails: The Data Is Brutal
I'm not selling 4-day weeks. They broke my workflow 3 times:
- On-call week. Server panic on Friday. I was "off". Worked 6 hours anyway. Result: 5-day week + guilt + broken family time. Net negative.
- Upstream dependency. My colleague ships on Fridays. I was blocked every Monday until he replied. Lost 20% of Mon to context-switching.
- Crunch time. 2 weeks before a demo, I switched back to 7 days. 4-day weeks are for marathons. Sprints need all hands.
External data backs this up:
- Cambridge University 2022: 61 companies, 6 month trial. Burnout -71%, Revenue +1.4%. You feel better. The company doesn't print money.
- Buffer 2020: Tried 4-day for engineers. Rolled back. Reason: collaboration overhead killed flow.
- Microsoft Japan 2019: +40% sales productivity. But they were sales, not engineers building databases.
The Actual Takeaway: Maker Schedule, Not 4-Day Week
Don't ask your boss for a 4-day workweek. Ask for this:
- Block 4 days. No meetings. No Slack. No code review. Just creation.
- Take 3 days off. Really off. No laptop. Your L3 cache needs it.
- Rotate on-call. Pay them 2x. A 4-day week with on-call is just a 5-day week with lies.
If you can't get #1, a 4-day week will make you slower.
If you can, your git log might look like mine.
My boss didn't give me a 4-day week. I gave it to myself. I tracked the data.
And for this project, alone, writing C++, the data says it worked.
Your codebase is different. Your team is different.
Don't trust me. Trust your git log.
Repo: github.com/yasha1971-coder/glyph-engine
Traffic: 1,043 clones in 14 days during this experiment.