Ask staff what they do with the fifth day and you will hear an unglamorous list: sleep, laundry, a dentist appointment that no longer costs annual leave, the school run without sprinting, caring for a parent, nothing at all. Occasionally you will also hear about paid work for someone else. How an employer responds to that list decides whether the day off delivers its main benefit or quietly cancels it.
The benefit, the evidence keeps saying, is recovery. The moment you start policing how adults recover, you have taken the recovery away and replaced it with a compliance exercise.
What the day is actually for
In the big pilots, staff consistently report using the day for rest, household and caring responsibilities, health appointments, exercise and study. In the UK trial, 60 percent of staff found it easier to combine work with care responsibilities, and wellbeing gains tracked how much people’s hours genuinely fell. The mechanism researchers keep identifying is not mysterious: less fatigue, better sleep, more sense of control over the week.
Notice what is not on the list: producing more for the employer. A day off that only “works” if staff spend it becoming better employees is a training day with better marketing. The deal in a 100-80-100 model is that the organisation gets 100 percent of output in 80 percent of time. What happens in the other 20 percent belongs to the employee.
It helps to say that out loud, in writing, at the start of a pilot — because staff will not assume it. Many will spend their first few Fridays half-expecting to be judged, and some will log on “just to check,” which is how a day off becomes an unpaid on-call day.
The second-job question, answered like an adult
Sooner or later a manager asks: what if someone works another job on their day off? The honest answer has three parts.
First, most employment arrangements already deal with this. Contracts commonly require disclosure of outside work, and the legitimate employer interests are narrow and nameable: conflicts of interest, confidentiality, safety-critical fatigue, and total working-time limits where the law imposes them. Those interests justify a disclosure rule. They do not justify a general power to approve how someone spends their own time.
Second, scale matters. A few hours of freelance work a month is not the same as a second full-time job, and treating them identically will drive the small, harmless cases underground while doing nothing about the genuinely risky ones. If someone is exhausted, that is a performance and wellbeing conversation you can have with evidence — actual hours, actual output, actual signs of fatigue — regardless of what caused it.
Third, look in the mirror before you look at the employee. The commonest reason staff fill a day off with paid work is that they need the money, which is a pay conversation, or that their workload never really fell, which is a design failure. In pilot after pilot, the “secret working” problem that actually damaged results was staff working for their own employer on the day off, unpaid, because the work had not been redesigned. Police that if you must police anything.
Protecting rest without a rulebook
You cannot mandate recovery, and you should not try. What you can do is remove the things that destroy it.
Keep the day genuinely off: no routine meetings, no “quick calls,” no expectation of inbox monitoring, and an out-of-office that routes to a named person rather than a void. Make sure taking the day is not quietly penalised in how work is allocated on the other four. And have leaders take their own day visibly — staff calibrate what is safe from what managers do, not from what the policy says.
It is also worth naming, early, that rest includes doing nothing productive and not reporting back on it. Some organisations, keen to evidence the benefit, survey staff on how they used the day in such detail that the day starts to feel audited. Ask about rest, fatigue and whether the day felt like their own. Leave the itinerary alone.
A short conversation worth having with your team
Before launch, agree three things together: the day is yours and the organisation will not monitor how you spend it; outside-work disclosure rules, where they exist, still apply and here is exactly what they cover; and if the day keeps getting eaten by this organisation’s work, that is a pilot problem to raise, not a personal failure to hide.
That is the whole design. A day off that people can actually use — for rest, for life admin, for family, occasionally for other work within the normal rules — is what produces the recovery the business case depends on. Protect the boundary, trust adults with the rest, and spend your management energy on the workload that keeps trying to cross it.
Sources
- Autonomy / University of Cambridge / Boston College, UK 2022 pilot results, reported 21 Feb 2023 — https://www.sciencedaily.com/releases/2023/02/230221113132.htm
- Fan, Schor, Kelly & Gu (2025), Nature Human Behaviour four-day-week study, reported 22 Jul 2025 — https://www.beckershospitalreview.com/workforce/4-day-workweek-boosts-employee-well-being-study/
- University of Münster, Germany 2024 four-day-week pilot, reported Oct 2024 — https://phys.org/news/2024-10-hours-germany-wide.amp
Day5Group is a consultancy that assists in the transition to a 4 day work week. More about Day5Group · All blog articles