# Summary of Proposal When using specifically the `gregorian` calendar attribute with time coordinates, restrict the time range to only dates in the real-world Gregorian calendar. That is, date/times no earlier than 1582 October 15 00:00:00.
Usage for dates earlier than the Julian/Gregorian crossover of 1582 October 15 is deprecated but not prohibited, because of possible usage in existing data sets. The initial proposal is to add this restriction to the `gregorian` label, but leave the `standard` and CF default (unspecified) calendars unchanged. Until now, `gregorian` and `standard` were both synonyms for the default mixed Julian/Gregorian calendar as defined by UDUNITS, and in common usage with netCDF since the 1990's. This proposal would split `gregorian` and `standard` into two separate calendar definitions in [CF section 4.4.1](https://urldefense.us/v3/__https://cfconventions.org/Data/cf-conventions/cf-conventions-1.8/cf-conventions.html*calendar__;Iw!!G2kpM7uM-TzIFchu!iBErcBI6ZCO_WSyPGeut17gWLz8v9vAkoS-pe-fxHgHknladMXlS1qLRmN-VWcV2sw3FoOO-cq0$ ). This is a recurring request, such as in issues #148 and #298, and at other times. Reference: [Wikipedia article "Gregorian calendar"](https://urldefense.us/v3/__https://en.wikipedia.org/wiki/Gregorian_calendar__;!!G2kpM7uM-TzIFchu!iBErcBI6ZCO_WSyPGeut17gWLz8v9vAkoS-pe-fxHgHknladMXlS1qLRmN-VWcV2sw3Fdhh9bdU$ ) # Details Same as in the proposal for #298, this restriction on dates would apply to both the reference date/time string, and to encoded date/time values. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://urldefense.us/v3/__https://github.com/cf-convention/cf-conventions/issues/319__;!!G2kpM7uM-TzIFchu!iBErcBI6ZCO_WSyPGeut17gWLz8v9vAkoS-pe-fxHgHknladMXlS1qLRmN-VWcV2sw3FaxvXD5Q$ 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].
