fix: declare a unit when creating NaT datetime

d-v-b · d-v-b · commit 70839853b9d7 · 2026-04-22T14:55:14.000+02:00
diff --git a/src/zarr/core/dtype/npy/time.py b/src/zarr/core/dtype/npy/time.py
@@ -851,7 +851,7 @@ def default_scalar(self) -> np.datetime64:
             The default scalar value, which is a 'Not-a-Time' (NaT) value
         """
 
-        return np.datetime64("NaT")
+        return np.datetime64("NaT", self.unit)
 
     def from_json_scalar(self, data: JSON, *, zarr_format: ZarrFormat) -> np.datetime64:
         """
diff --git a/tests/test_dtype/test_npy/test_time.py b/tests/test_dtype/test_npy/test_time.py
@@ -66,7 +66,7 @@ class TestDateTime64(_TestTimeBase):
     cast_value_params = (
         (DateTime64(unit="Y", scale_factor=1), "1", np.datetime64("1", "Y")),
         (DateTime64(unit="s", scale_factor=1), "2005-02-25", np.datetime64("2005-02-25", "s")),
-        (DateTime64(unit="ns", scale_factor=1), "NaT", np.datetime64("NaT")),
+        (DateTime64(unit="ns", scale_factor=1), "NaT", np.datetime64("NaT", "ns")),
     )
     invalid_scalar_params = (
         (DateTime64(unit="Y", scale_factor=1), 1.3),

Original file line number	Diff line number	Diff line change
`@@ -66,7 +66,7 @@ class TestDateTime64(_TestTimeBase):`
`66`	`66`	`cast_value_params = (`
`67`	`67`	`(DateTime64(unit="Y", scale_factor=1), "1", np.datetime64("1", "Y")),`
`68`	`68`	`(DateTime64(unit="s", scale_factor=1), "2005-02-25", np.datetime64("2005-02-25", "s")),`
`69`		`- (DateTime64(unit="ns", scale_factor=1), "NaT", np.datetime64("NaT")),`
	`69`	`+ (DateTime64(unit="ns", scale_factor=1), "NaT", np.datetime64("NaT", "ns")),`
`70`	`70`	`)`
`71`	`71`	`invalid_scalar_params = (`
`72`	`72`	`(DateTime64(unit="Y", scale_factor=1), 1.3),`