CalendarDateTime served a purpose in the early days of nc-time-axis, but I now think it may not be needed anymore, particularly once #75 is addressed (#80). cftime.datetime instances now have a meaningful calendar attribute and their comparisons now check that calendars and datetime components are equal. Should we include a DeprecationWarning in the next release of nc-time-axis?

As an aside, reading some of the existing tests for CalendarDateTime makes me a little uneasy now that cftime.datetime objects have a default calendar of "gregorian" instead of None:

Apparently these still pass despite the fact that the calendar of the datetime object does not match the calendar of the CalendarDateTime object.