Different claims need different evidence
The sources below study working time, well-being, or measurement. None of them is a trial of the Metric Calendar. They help frame questions about schedules; they do not establish the value of ten months, six-day metric weeks, or Bonus Rest Days.
240 Focus Days in a year
Ten months × six metric weeks × four Focus Days. This follows from the specification and can be checked without a workplace study.
Working-time changes can affect well-being
Selected shorter-working-time interventions report improvements in participating workers. Their settings, policies, and evaluation designs matter.
More predictable planning and recovery
The proposal aims to make work/rest patterns and month layouts easier to anticipate. That intention is not an observed outcome.
Better outcomes under this calendar
Whether this specific arrangement improves health, productivity, coordination, or satisfaction needs direct evaluation.
Research and primary sources
This is a focused reading list, not a systematic review. Sources were checked on September 19, 2026. Each summary identifies what the source supports and the limit of its relevance to this project.
The UK four-day week pilot
The report covers 61 companies and about 2,900 workers in a 2022 trial. Organisations prepared for reduced working time, retained pay, and used different scheduling approaches. The report describes improvements in employee well-being.
Relevance: work redesign and preparation deserve attention when evaluating schedule changes. Limit: these participating organisations were testing reduced working time, not a six-day calendar cycle. The results cannot be treated as a general guarantee.
Autonomy and research partners. The results are in: the UK’s four-day week pilot. 2023. Read the report and findings ↗
Iceland’s shorter working-time trials
Haraldsson and Kellam analyse two trials conducted in 2015–2019, covering around 2,500 workers and 35–36-hour working weeks without reduced pay. They report that productivity and service provision were maintained or improved in most participating workplaces, alongside well-being improvements.
Relevance: the report offers examples of adapting service delivery to shorter hours. Limit: it evaluates particular public-sector changes and does not compare alternative calendar structures.
Guðmundur D. Haraldsson and Jack Kellam. Going Public: Iceland’s Journey to a Shorter Working Week. Autonomy / Alda, 2021. Read the report and findings ↗
Reduced working time and worker well-being
A study in Nature Human Behaviour reports improvements in worker well-being under an income-preserving four-day-workweek intervention. The publication highlights job satisfaction, mental and physical health, and burnout.
Relevance: it supports investigating how working-time changes relate to worker outcomes. Limit: it does not test the Metric Calendar or establish that a four-in-six pattern produces the same effects. The summary here is limited to the publisher’s public description.
Fan et al. Work time reduction via a 4-day workweek finds improvements in workers’ well-being. Nature Human Behaviour, 2025. DOI: 10.1038/s41562-025-02259-6. Publication record ↗ · Publisher’s study summary ↗
Long working hours and health
WHO and ILO report that working at least 55 hours per week is associated with a higher risk of stroke and death from ischaemic heart disease than working 35–40 hours per week.
Relevance: actual hours and health outcomes matter when evaluating a schedule. Limit: a change in calendar labels alone does not reduce exposure to long hours, and this analysis does not identify an optimal calendar or work/rest cycle.
World Health Organization / International Labour Organization. Long working hours increasing deaths from heart disease and stroke. May 17, 2021. Read the findings and linked studies ↗
Output per hour is a separate measure
The OECD defines GDP per hour worked as a labour-productivity measure: output generated per hour of labour.
Relevance: evaluations should distinguish hours, total output, and output per hour. Limit: the indicator’s definition is not evidence that reducing hours preserves output, and an economy-wide measure is not a ready-made measure for every workplace.
OECD. GDP per hour worked. Read the indicator definition ↗
The Gregorian leap-year rule
The U.S. Naval Observatory documents the leap-year rule retained by this proposal: divisible by 4, except centuries not divisible by 400. This verifies the Gregorian rule; it is not an endorsement of Metric Calendar.
U.S. Naval Observatory. Leap Years and Introduction to Calendars. Leap-year rule ↗ · Calendar background ↗
What the evidence does not establish
- Calendar-specific effects. The cited studies do not isolate ten-month years, six-day metric weeks, or extra days outside a week.
- Transfer to every workplace. Participating organisations and interventions differ. Continuous services, irregular shifts, and hourly work require their own evaluation.
- Guaranteed productivity. Better well-being does not by itself demonstrate unchanged output, quality, staffing costs, or service access.
- Long-term compatibility. Family life, schooling, religious observance, international coordination, and existing software could make a new rhythm difficult to sustain.
- A complete evidence review. This selected bibliography cannot estimate the balance of all published and unpublished findings.
The site presents no documented Metric Calendar trial, adoption count, independent review, or institutional endorsement. The research cited belongs to its authors and concerns the interventions they actually studied.
A research agenda for the proposal
A useful evaluation would distinguish changing date labels from changing work schedules. They are separate interventions with different risks and costs.
- Understanding: can people read, convert, and schedule Metric dates accurately after a short introduction?
- Planning: does a repeatable layout reduce planning effort, or does maintaining dual dates increase it?
- Work and rest: how does a four-in-six cycle affect actual hours, fatigue, recovery, and preferences over time?
- Coordination and equity: who absorbs the costs of mismatched weekends, care commitments, staffing, and technical changes?
- Service and output: what happens to total output, quality, errors, waiting times, and cost per unit of service?
Specify the baseline, participation rules, outcome measures, and stopping criteria before a trial. Report negative and neutral outcomes as well as positive ones. See the pilot evaluation guidance.
Citing this project
Use the specification for claims about the calendar’s rules, this page for the project’s interpretation of research, and the original publications for empirical findings.
Sections have stable links, such as Bonus days and leap years and Limits of the evidence. The source repository records changes to this living site.