I initially liked Jonathan's idea of introducing a new proleptic calendar(s) to make it explicit when people care about the interpretation of negative years in the reference time, but, after thinking over the point discussed below, I would prefer to use a qualifier, e.g. `proleptic_gregorian cardinal`
If you take an etymological approach, I think `AD 1` refers, in effect, to "year 1": i.e. it is a reference of a time period, not a point in time. Similarly, `1 BC` is "year 1 before". From that perspective, it is natural that there is no `AD 0` or `0 BC`. UTC adopts the convention that `2020-01-01 00:00:00` refers to the start of AD 2020, but says nothing about negative times. The question, I think, is not "Is there a year zero in the calendar?" but rather "How do we encode a given calendar year in the time stamp?". Given that positive `YYYY` in the datestamp is universally understood to refer to `AD YYYY`, arguments can be made for interpreting `-YYYY` as either and extension backwards treating the years as a sequence of integers, or as `1 BC`. This is an encoding choice. For this reason, I would not modify the calendar, but instead add an optional qualifier to identify the convention for encoding BC years in the timestamp. I'm not sure whether there is a good mnemonic term, but I suggest `proleptic_gregorian cardinal` to refer to use of cardinals, `-1, 0, 1` rather than ordinals, `2nd before`, `1st before`, `1st after`. -- 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-697981313 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].
