fix for issue #354

Changelog

@@ -1,3 +1,8 @@
+since version 1.6.4 release
+===========================
+* roundtrip not correct when dates are all python datetime
+  instances and calendar not proleptic_gregorian (issue #354).
+
 version 1.6.4 (release tag v1.6.4rel)
 =====================================
  * build aarch64 linux wheels (issue #333).

src/cftime/_cftime.pyx

@@ -40,7 +40,7 @@ cdef int[12] _dayspermonth_leap = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 3
 cdef int[13] _cumdayspermonth = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365]
 cdef int[13] _cumdayspermonth_leap = [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366]
 
-__version__ = '1.6.4.post1'
+__version__ = '1.6.5'
 
 # Adapted from http://delete.me.uk/2005/03/iso8601.html
 # Note: This regex ensures that all ISO8601 timezone formats are accepted - but, due to legacy support for other timestrings, not all incorrect formats can be rejected.
@@ -261,7 +261,7 @@ def date2num(dates, units, calendar=None, has_year_zero=None, longdouble=False):
     if unit in ["months", "month"] and calendar != "360_day":
         raise ValueError("Units of months only valid for 360_day calendar.")
     unit_timedelta = timedelta(microseconds=UNIT_CONVERSION_FACTORS[unit])
-    can_use_python_basedatetime = _can_use_python_datetime(basedate,calendar)
+    can_use_python_basedatetime = calendar=='proleptic_gregorian' and _can_use_python_datetime(basedate,calendar)
 
     if can_use_python_basedatetime and all_python_datetimes:
         use_python_datetime = True

test/test_cftime.py

@@ -943,6 +943,16 @@ def roundtrip(delta,eps,units):
         times = np.array([1,2,3,np.inf],dtype=np.float64)
         result = cftime.num2date(times, 'days since 2000-01-01', 'standard')
         np.testing.assert_equal(result, expected)
+        # issue #354: roundtrip not correct when dates are all python datetime
+        # instances and calendar not proleptic_gregorian.
+        datesin = np.array(["0002"],
+                  dtype="datetime64[s]").astype("M8[us]").astype(datetime)
+        datein = datesin.item()
+        num = cftime.date2num(datein, "seconds since 2000-01-01", calendar='standard')
+        dateout = cftime.num2date(num, "seconds since 2000-01-01", calendar='standard')
+        dateout2 = cftime.datetime(datein.year, datein.month, datein.day,
+                   calendar='standard')
+        assert(dateout==dateout2)
 
 
 class TestDate2index(unittest.TestCase):