I can easily think of two other very commonly-used calendars that do not fit {year, month, day}:
- The Julian Day and Rata Die calendars we talked about in this topic, which only count days.
- The ISO Week date calendar, that is used a lot in business and fiscal environments, which counts
{year, week_number, day}.
Besides this, there are many calendars that do not fit the DateTime subdivision in hours/minutes/seconds/milliseconds, such as (from the top of my head; there are more):
- Rata Die, which counts a fraction of a day and is therefore precise.
- The afore-mentioned Hebrew calendar, which uses 12 hours that are each subdivided in 1080 ‘parts’, a day thus contains 25920 parts.
- The Hindu calendar, which subdivides a day into 60 Ghati and a Ghati into 60 Pala.
- TAI, which only counts seconds.
- POSIX time, which only counts seconds but gets corrected for leap seconds.
