Series datetime is_year_end and is_year_start (#8954)

This PR aims to allow users to be able to determine whether a datetime is the beginning or end of a year. This PR closes #8680

Authors:
  - Marlene  (https://github.com/marlenezw)
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)
  - https://github.com/brandon-b-miller

URL: #8954

python/cudf/cudf/core/series.py

@@ -6082,6 +6082,76 @@ def is_month_end(self):
         )
         return (self.day == last_day.dt.day).fillna(False)
 
+    @property
+    def is_year_start(self):
+        """
+        Boolean indicator if the date is the first day of the year.
+
+        Returns
+        -------
+        Series
+        Booleans indicating if dates are the first day of the year.
+
+        Example
+        -------
+        >>> import pandas as pd, cudf
+        >>> s = cudf.Series(pd.date_range("2017-12-30", periods=3))
+        >>> dates
+        0   2017-12-30
+        1   2017-12-31
+        2   2018-01-01
+        dtype: datetime64[ns]
+        >>> dates.dt.is_year_start
+        0    False
+        1    False
+        2    True
+        dtype: bool
+        """
+        outcol = self.series._column.get_dt_field(
+            "day_of_year"
+        ) == cudf.Scalar(1)
+        return Series._from_data(
+            {None: outcol.fillna(False)},
+            index=self.series._index,
+            name=self.series.name,
+        )
+
+    @property
+    def is_year_end(self):
+        """
+        Boolean indicator if the date is the last day of the year.
+
+        Returns
+        -------
+        Series
+        Booleans indicating if dates are the last day of the year.
+
+        Example
+        -------
+        >>> import pandas as pd, cudf
+        >>> dates = cudf.Series(pd.date_range("2017-12-30", periods=3))
+        >>> dates
+        0   2017-12-30
+        1   2017-12-31
+        2   2018-01-01
+        dtype: datetime64[ns]
+        >>> dates.dt.is_year_end
+        0    False
+        1     True
+        2    False
+        dtype: bool
+        """
+        day_of_year = self.series._column.get_dt_field("day_of_year")
+        leap_dates = libcudf.datetime.is_leap_year(self.series._column)
+
+        leap = day_of_year == cudf.Scalar(366)
+        non_leap = day_of_year == cudf.Scalar(365)
+        result = cudf._lib.copying.copy_if_else(leap, non_leap, leap_dates)
+        result = result.fillna(False)
+        return Series._from_data(
+            {None: result}, index=self.series._index, name=self.series.name,
+        )
+
     def _get_dt_field(self, field):
         out_column = self.series._column.get_dt_field(field)
         return Series(

python/cudf/cudf/tests/test_datetime.py

@@ -1409,3 +1409,69 @@ def test_is_month_end(data, dtype):
     got = gs.dt.is_month_end
 
     assert_eq(expect, got)
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        [
+            "2020-05-31",
+            None,
+            "1999-12-01",
+            "2000-12-21",
+            None,
+            "1900-01-01",
+            "1800-03-14",
+            "2100-03-10",
+            "1970-01-01",
+            "1969-12-11",
+            "2017-12-30",
+            "2017-12-31",
+            "2018-01-01",
+        ]
+    ],
+)
+@pytest.mark.parametrize("dtype", ["datetime64[ns]"])
+def test_is_year_start(data, dtype):
+    ps = pd.Series(data, dtype=dtype)
+    gs = cudf.from_pandas(ps)
+
+    expect = ps.dt.is_year_start
+    got = gs.dt.is_year_start
+
+    assert_eq(expect, got)
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        [
+            "2020-05-31",
+            None,
+            "1999-12-01",
+            "2000-12-21",
+            None,
+            "1900-12-31",
+            "1800-03-14",
+            "2017-12-30",
+            "2017-12-31",
+            "2020-12-31 08:00:00",
+            None,
+            "1999-12-31 18:40:00",
+            "2000-12-31 04:00:00",
+            None,
+            "1800-12-14 07:30:00",
+            "2100-12-14 07:30:00",
+            "2020-05-31",
+        ]
+    ],
+)
+@pytest.mark.parametrize("dtype", ["datetime64[ns]"])
+def test_is_year_end(data, dtype):
+    ps = pd.Series(data, dtype=dtype)
+    gs = cudf.from_pandas(ps)
+
+    expect = ps.dt.is_year_end
+    got = gs.dt.is_year_end
+
+    assert_eq(expect, got)