diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py index 077bde35a4c94..e0a4587535cfd 100644 --- a/pandas/core/arrays/datetimes.py +++ b/pandas/core/arrays/datetimes.py @@ -2119,6 +2119,32 @@ def isocalendar(self) -> DataFrame: >>> idx.is_year_start array([False, False, True]) + + This method, when applied to Series with datetime values under + the ``.dt`` accessor, will lose information about Business offsets. + + >>> dates = pd.Series(pd.date_range("2020-10-30", periods=4, freq="BYS")) + >>> dates + 0 2021-01-01 + 1 2022-01-03 + 2 2023-01-02 + 3 2024-01-01 + dtype: datetime64[ns] + + >>> dates.dt.is_year_start + 0 True + 1 False + 2 False + 3 True + dtype: bool + + >>> idx = pd.date_range("2020-10-30", periods=4, freq="BYS") + >>> idx + DatetimeIndex(['2021-01-01', '2022-01-03', '2023-01-02', '2024-01-01'], + dtype='datetime64[ns]', freq='BYS-JAN') + + >>> idx.is_year_start + array([ True, True, True, True]) """, ) is_year_end = _field_accessor(