issues: 408772665

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
408772665 MDU6SXNzdWU0MDg3NzI2NjU= 2761 'standard' calendar refers to 'proleptic_gregorian' in cftime_range rather than 'gregorian' 6628425 closed 0     2 2019-02-11T13:06:05Z 2019-02-15T21:58:16Z 2019-02-15T21:58:16Z MEMBER      

Code Sample, a copy-pastable example if possible

```python In [1]: import xarray

In [2]: xarray.cftime_range('2000', periods=3, calendar='standard').values Out[2]: array([cftime.DatetimeProlepticGregorian(2000, 1, 1, 0, 0, 0, 0, -1, 1), cftime.DatetimeProlepticGregorian(2000, 1, 2, 0, 0, 0, 0, -1, 1), cftime.DatetimeProlepticGregorian(2000, 1, 3, 0, 0, 0, 0, -1, 1)], dtype=object) ```

Problem description

When writing cftime_range I used dates from a proleptic Gregorian calendar when the calendar type was specified as 'standard'. While this is consistent with Python's built-in datetime.datetime (which uses a proleptic Gregorian calendar), this differs from the behavior in cftime.num2date and ultimately the CF conventions, which state that 'standard' should refer to the true Gregorian calendar. My inclination is that considering "cf" is in the name of cftime_range, we should adhere to those conventions as closely as possible (and hence the way I initially coded things was a mistake).

Expected Output

python In [2]: xarray.cftime_range('2000', periods=3, calendar='standard').values Out[2]: array([cftime.DatetimeGregorian(2000, 1, 1, 0, 0, 0, 0, -1, 1), cftime.DatetimeGregorian(2000, 1, 2, 0, 0, 0, 0, -1, 1), cftime.DatetimeGregorian(2000, 1, 3, 0, 0, 0, 0, -1, 1)], dtype=object)

Do others agree that we should fix this? If we were to make this change, would it be appropriate to consider it a bug and simply make the breaking change immediately, or might we need a deprecation cycle?

 
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