BUG: DateOffset(normalize=True).rollback (#62910)

Author: jbrockmendel

doc/source/whatsnew/v3.0.0.rst

@@ -980,6 +980,7 @@ Datetimelike
 - Bug in :meth:`DataFrame.fillna` raising an ``AssertionError`` instead of ``OutOfBoundsDatetime`` when filling a ``datetime64[ns]`` column with an out-of-bounds timestamp. Now correctly raises ``OutOfBoundsDatetime``. (:issue:`61208`)
 - Bug in :meth:`DataFrame.min` and :meth:`DataFrame.max` casting ``datetime64`` and ``timedelta64`` columns to ``float64`` and losing precision (:issue:`60850`)
 - Bug in :meth:`Dataframe.agg` with df with missing values resulting in IndexError (:issue:`58810`)
+- Bug in :meth:`DateOffset.rollback` (and subclass methods) with ``normalize=True`` rolling back one offset too long (:issue:`32616`)
 - Bug in :meth:`DatetimeIndex.is_year_start` and :meth:`DatetimeIndex.is_quarter_start` does not raise on Custom business days frequencies bigger then "1C" (:issue:`58664`)
 - Bug in :meth:`DatetimeIndex.is_year_start` and :meth:`DatetimeIndex.is_quarter_start` returning ``False`` on double-digit frequencies (:issue:`58523`)
 - Bug in :meth:`DatetimeIndex.union` and :meth:`DatetimeIndex.intersection` when ``unit`` was non-nanosecond (:issue:`59036`)

pandas/_libs/tslibs/offsets.pyx

@@ -692,6 +692,9 @@ cdef class BaseOffset:
             Rolled timestamp if not on offset, otherwise unchanged timestamp.
         """
         dt = Timestamp(dt)
+        if self.normalize and (dt - dt.normalize())._value != 0:
+            # GH#32616
+            dt = dt.normalize()
         if not self.is_on_offset(dt):
             dt = dt - type(self)(1, normalize=self.normalize, **self.kwds)
         return dt

pandas/tests/tseries/offsets/test_offsets.py

@@ -431,22 +431,6 @@ def test_rollback(self, offset_types):
         for k in norm_expected:
             norm_expected[k] = Timestamp(norm_expected[k].date())
 
-        normalized = {
-            "Day": Timestamp("2010-12-31 00:00:00"),
-            "DateOffset": Timestamp("2010-12-31 00:00:00"),
-            "MonthBegin": Timestamp("2010-12-01 00:00:00"),
-            "SemiMonthBegin": Timestamp("2010-12-15 00:00:00"),
-            "YearBegin": Timestamp("2010-01-01 00:00:00"),
-            "HalfYearBegin": Timestamp("2010-07-01 00:00:00"),
-            "Week": Timestamp("2010-12-25 00:00:00"),
-            "Hour": Timestamp("2011-01-01 00:00:00"),
-            "Minute": Timestamp("2011-01-01 00:00:00"),
-            "Second": Timestamp("2011-01-01 00:00:00"),
-            "Milli": Timestamp("2011-01-01 00:00:00"),
-            "Micro": Timestamp("2011-01-01 00:00:00"),
-        }
-        norm_expected.update(normalized)
-
         sdt = datetime(2011, 1, 1, 9, 0)
         ndt = np.datetime64("2011-01-01 09:00")