Dear @Dave-Allured et al. We must have had a similar discussion some time ago - it feels familiar! While I appreciate wanting to avoid the Julian-Gregorian transition, I don't think we should disallow the default/`standard` calendar before 1582. This calendar has always been clearly defined as the _mixed_ Julian/Gregorian calendar; it's the real-world calendar, and we can't exclude a need for real-world time axes which cross the transition.
The Gregorian calendar is undefined before 1582. Possibly we could redefine `gregorian` in the way Dave suggests (not allowing encoded dates or reference dates before 1582). That would give it a different meaning from default/`standard` in future data. This change could be a pitfall for interpretating any existing data which says `calendar="gregorian"` for time coordinates before 1582, but I think `gregorian` is less likely to have been used than `standard` or default since it is truly _not_ Gregorian for such times! However, in view of this point of Dave's, I'd like to change my proposal for new calendar names to: * `mixed_withzero`, in which year 0 means 1 BC, and any year is allowed. * `mixed_nozero`, in which year -1 means 1 BC, year 0 is not allowed in the reference date, and dates in year 0 cannot be encoded. For years>0, both of these calendars are the same as the default/`standard` calendar. In that calendar, years<1 should be deprecated. For `julian` and `proleptic_gregorian`, years before 1 should be deprecated, and we could define `_withzero` and `_nozero` variants correspondingly if they are needed. For `noleap`=`365_day`, `all_leap`=`366_day` and `360_day`, I think we could assume that year zero and negative years are allowed. The current definitions describe them as "Gregorian" calendars, which isn't really a useful statement! I would redefine them as calendars in which months have the same lengths in every year. In `noleap`, the month lengths are as for a non-leap year of the Gregorian calendar, in `all_leap`, they are as for a leap year, and in `360_day` all months have 30 days. Best wishes Jonathan -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/issues/298#issuecomment-698987558 This list forwards relevant notifications from Github. It is distinct from [email protected], although if you do nothing, a subscription to the UCAR list will result in a subscription to this list. To unsubscribe from this list only, send a message to [email protected].
