arr = pd.array( ["2017-01-01", "2018-01-01", "2019-01-01"], dtype="date32[day][pyarrow]" ) cats = pd.Index(['2017-01-01', '2018-01-01', '2019-01-01'], dtype="M8[s]") dtype = pd.CategoricalDtype(cats, ordered=False) arr.astype(cats.dtype) # <- works arr.astype(dtype) # <- all-NaT arr = pd.core.arrays.ArrowExtensionArray._from_sequence(["1h", "2h", "3h"]) cats = pd.Index(['1h', '2h', '3h'], dtype="m8[ns]") dtype = pd.CategoricalDtype(cats, ordered=False) arr.astype(cats.dtype) # <- works arr.astype(dtype) # <- all-NaT