Calendar specification
What is the Metric Calendar?
The Metric Calendar is a proposed ten-month calendar with six-day metric weeks, five annual Bonus Rest Days, and the Gregorian leap-year rule. It keeps the Gregorian year number and starts each year on the same day as Gregorian January 1.
Each month contains six complete metric weeks: 36 regular days. Days 1–4 of each metric week are Focus Days (also called Focus/Work Days); days 5–6 are Rest Days. These are designations in the proposal, not automatic changes to anyone’s employment schedule.
10 months × 6 metric weeks × 6 days = 360 regular days.
360 + 5 Bonus Rest Days = 365.
A leap year adds one Leap Day = 366.
This page states the rules used by the converter. The diagrams illustrate those rules; they do not introduce a different calendar model.
The ten metric months
Months use the numbers 01–10. Odd-numbered months have 36 days; even-numbered months have 37, except month 10 has 38 in a leap year. All months begin with Focus Day 1.
| Metric month | Days | Day of year | After the six weeks |
|---|---|---|---|
| 01 | 36 | 1–36 | — |
| 02 | 37 | 37–73 | Bonus Rest Day |
| 03 | 36 | 74–109 | — |
| 04 | 37 | 110–146 | Bonus Rest Day |
| 05 | 36 | 147–182 | — |
| 06 | 37 | 183–219 | Bonus Rest Day |
| 07 | 36 | 220–255 | — |
| 08 | 37 | 256–292 | Bonus Rest Day |
| 09 | 36 | 293–328 | — |
| 10 | 37 / 38 | 329–365 / 366 | Bonus Rest Day; then Leap Day in leap years |
The ordinal ranges stay the same in leap years until the final day is added to month 10. Their corresponding Gregorian dates can differ after February.
The six-day metric week
For a regular metric day d (1–36), its position in the metric week is ((d − 1) mod 6) + 1. Its metric week within the month is ceil(d / 6). For example, month day 17 is the fifth day of metric week 3: Rest Day 1.
Bonus Rest Days and Leap Day have no metric week number or metric weekday. After an extra day, the next month starts a new metric week at Focus Day 1. Gregorian weekdays continue independently; metric Rest Days do not stay on Saturday and Sunday.
Bonus days, leap years, and year-end
Five Bonus Rest Days
Day 37 of every even-numbered month is a Bonus Rest Day. It belongs to that month but sits outside its six metric weeks. A common year ends with the Bonus Rest Day YYYY-10-37, which is also New Year’s Eve.
The leap-year rule
A year is a leap year if divisible by 4, except century years must also be divisible by 400. Thus 2000 and 2028 are leap years; 1900 and 2100 are common years. This is the Gregorian rule documented by the U.S. Naval Observatory.
In a leap year, month 10 ends with YYYY-10-38, designated Leap Day / New Year’s Eve. Day 37 remains a Bonus Rest Day but is no longer New Year’s Eve. Leap Day is separate from both the regular metric weeks and the five Bonus Rest Days.
Conversion preserves the day’s position in the year. For example, g2028-02-29 = 2028-02-24, while g2028-12-31 = 2028-10-38. See the conversion method.
How to write a date
Write a Metric date as YYYY-MM-DD, without a prefix. In this project’s notation, a Gregorian date starts with a lowercase g: gYYYY-MM-DD. The prefix is a project convention, not a standard Gregorian date format.
2026-05-36- Year 2026, metric month 05, day 36.
g2026-07-01- Gregorian July 1, 2026: the same day.
Always label the calendar when context could be unclear. A Metric date such as 2026-02-37 is valid here but is not a valid Gregorian date for a standard date field.
The converter supports years 0001–9999, without a year zero. It applies the Gregorian rules to all supported years (the proleptic Gregorian calendar). It does not model historical local calendar changes. The year range is a tool limit, not an added calendar rule.
What the year adds up to
| Day type | Common year | Leap year |
|---|---|---|
| Focus Days | 240 | 240 |
| Regular Rest Days | 120 | 120 |
| Bonus Rest Days | 5 | 5 |
| Leap Day | 0 | 1 |
| Total | 365 | 366 |
The calendar has 60 complete metric weeks every year. Actual working hours, pay, public holidays, and service rosters require separate decisions.