Ranges starting on 0001-01-01 seem to not be valid

[ecmwf-cobarzan]

Ranges starting on 0001-01-01 seem to not be valid, even though otherwise working:

>>> from datetimerange import DateTimeRange
>>> s = "0001-01-01"
>>> e = "2026-01-10"
>>> r = DateTimeRange(s,e)
>>> r
0001-01-01T00:00:00 - 2026-01-10T00:00:00
>>> r.start_datetime
datetime.datetime(1, 1, 1, 0, 0)
>>> r.end_datetime
datetime.datetime(2026, 1, 10, 0, 0)
>>> r.is_valid_timerange()
False

The same works as expected for 0001-01-02 though (i.e. the interval is valid).