diff --git a/cf_units/__init__.py b/cf_units/__init__.py
index d0d3fe1a..e1c94f8c 100644
--- a/cf_units/__init__.py
+++ b/cf_units/__init__.py
@@ -403,20 +403,14 @@ def _discard_microsecond(date):
         datetime, or numpy.ndarray of datetime object.
 
     """
-    dates = np.asarray(date)
+    dates = np.asanyarray(date)
     shape = dates.shape
     dates = dates.ravel()
-    # Create date objects of the same type returned by cftime.num2date()
-    # (either datetime.datetime or cftime.datetime), discarding the
-    # microseconds
-    dates = np.array(
-        [
-            d
-            and d.__class__(d.year, d.month, d.day, d.hour, d.minute, d.second)
-            for d in dates
-        ]
-    )
+
+    # using the "and" pattern to support masked arrays of datetimes
+    dates = np.array([dt and dt.replace(microsecond=0) for dt in dates])
     result = dates[0] if shape == () else dates.reshape(shape)
+
     return result
 
 
diff --git a/cf_units/tests/unit/test__discard_microsecond.py b/cf_units/tests/unit/test__discard_microsecond.py
new file mode 100644
index 00000000..3ed578fd
--- /dev/null
+++ b/cf_units/tests/unit/test__discard_microsecond.py
@@ -0,0 +1,122 @@
+# Copyright cf-units contributors
+#
+# This file is part of cf-units and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
+"""Unit tests for the `cf_units._discard_microsecond` function."""
+
+import datetime
+import unittest
+
+import cftime
+import numpy as np
+import numpy.ma as ma
+
+from cf_units import _discard_microsecond as discard_microsecond
+
+
+class Test__datetime(unittest.TestCase):
+    def setUp(self):
+        self.kwargs = dict(year=1, month=2, day=3, hour=4, minute=5, second=6)
+        self.expected = datetime.datetime(**self.kwargs, microsecond=0)
+
+    def test_single(self):
+        dt = datetime.datetime(**self.kwargs, microsecond=7)
+        actual = discard_microsecond(dt)
+        self.assertEqual(self.expected, actual)
+
+    def test_multi(self):
+        shape = (5, 2)
+        n = np.prod(shape)
+
+        dates = np.array(
+            [datetime.datetime(**self.kwargs, microsecond=i) for i in range(n)]
+        ).reshape(shape)
+        actual = discard_microsecond(dates)
+        expected = np.array([self.expected] * n).reshape(shape)
+        np.testing.assert_array_equal(expected, actual)
+
+
+class Test__cftime(unittest.TestCase):
+    def setUp(self):
+        self.kwargs = dict(year=1, month=2, day=3, hour=4, minute=5, second=6)
+        self.calendars = cftime._cftime._calendars
+
+    def test_single(self):
+        for calendar in self.calendars:
+            dt = cftime.datetime(**self.kwargs, calendar=calendar)
+            actual = discard_microsecond(dt)
+            expected = cftime.datetime(
+                **self.kwargs, microsecond=0, calendar=calendar
+            )
+            self.assertEqual(expected, actual)
+
+    def test_multi(self):
+        shape = (2, 5)
+        n = np.prod(shape)
+
+        for calendar in self.calendars:
+            dates = np.array(
+                [
+                    cftime.datetime(**self.kwargs, calendar=calendar)
+                    for i in range(n)
+                ]
+            ).reshape(shape)
+            actual = discard_microsecond(dates)
+            expected = np.array(
+                [
+                    cftime.datetime(
+                        **self.kwargs, microsecond=0, calendar=calendar
+                    )
+                ]
+                * n
+            ).reshape(shape)
+            np.testing.assert_array_equal(expected, actual)
+
+
+class Test__falsy(unittest.TestCase):
+    def setUp(self):
+        self.kwargs = dict(year=1, month=2, day=3, hour=4, minute=5, second=6)
+        self.calendar = "360_day"
+        microsecond = 7
+        self.cftime = cftime.datetime(
+            **self.kwargs, microsecond=microsecond, calendar=self.calendar
+        )
+        self.datetime = datetime.datetime(
+            **self.kwargs, microsecond=microsecond
+        )
+
+    def test_single__none(self):
+        self.assertIsNone(discard_microsecond(None))
+
+    def test_single__false(self):
+        self.assertFalse(discard_microsecond(False))
+
+    def test_multi__falsy(self):
+        falsy = np.array([None, False, 0])
+        actual = discard_microsecond(falsy)
+        np.testing.assert_array_equal(falsy, actual)
+
+    def test_masked(self):
+        data = [self.cftime, self.datetime, self.cftime, self.datetime]
+        mask = [1, 0, 0, 1]
+        dates = ma.masked_array(data, mask=mask)
+        actual = discard_microsecond(dates)
+        expected = np.array(
+            [
+                ma.masked,
+                datetime.datetime(**self.kwargs),
+                cftime.datetime(**self.kwargs, calendar=self.calendar),
+                ma.masked,
+            ]
+        )
+        self.assertEqual(expected.shape, actual.shape)
+        for i, masked in enumerate(mask):
+            if masked:
+                self.assertIs(expected[i], actual[i])
+            else:
+                self.assertEqual(expected[i], actual[i])
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/cf_units/tests/unit/unit/test_Unit.py b/cf_units/tests/unit/unit/test_Unit.py
index 1ff356b9..b226b87e 100644
--- a/cf_units/tests/unit/unit/test_Unit.py
+++ b/cf_units/tests/unit/unit/test_Unit.py
@@ -67,7 +67,7 @@ def test_non_gregorian_calendar_conversion_dtype(self):
             (np.float64, True),
             (np.int32, False),
             (np.int64, False),
-            (np.int, False),
+            (int, False),
         ):
             data = np.arange(4, dtype=start_dtype)
             u1 = Unit("hours since 2000-01-01 00:00:00", calendar="360_day")
diff --git a/pyproject.toml b/pyproject.toml
index a861757a..5f148c19 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -62,6 +62,7 @@ exclude = '''
     | build
     | dist
   )/
+  | _version.py
 )
 '''