BUG: Fix creating DatetimeIndex with BusinessHour Frequency

doc/source/whatsnew/v1.5.3.rst

@@ -30,7 +30,7 @@ Bug fixes
 - Bug in :meth:`.Styler.to_excel` leading to error when unrecognized ``border-style`` (e.g. ``"hair"``) provided to Excel writers (:issue:`48649`)
 - Bug when chaining several :meth:`.Styler.concat` calls, only the last styler was concatenated (:issue:`49207`)
 - Fixed bug when instantiating a :class:`DataFrame` subclass inheriting from ``typing.Generic`` that triggered a ``UserWarning`` on python 3.11 (:issue:`49649`)
--
+- Fixed bug in :class:`BusinessHour` that could cause creation of ``DatetimeIndex`` to fail (:issue:`#49835`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_153.other:

pandas/_libs/tslibs/offsets.pyx

@@ -1847,15 +1847,20 @@ cdef class BusinessHour(BusinessMixin):
         earliest_start = self.start[0]
         latest_start = self.start[-1]
 
+        if self.n == 0:
+            is_same_sign = sign > 0
+        else:
+            is_same_sign = self.n * sign >= 0
+
         if not self.next_bday.is_on_offset(other):
             # today is not business day
             other = other + sign * self.next_bday
-            if self.n * sign >= 0:
+            if is_same_sign:
                 hour, minute = earliest_start.hour, earliest_start.minute
             else:
                 hour, minute = latest_start.hour, latest_start.minute
         else:
-            if self.n * sign >= 0:
+            if is_same_sign:
                 if latest_start < other.time():
                     # current time is after latest starting time in today
                     other = other + sign * self.next_bday

pandas/tests/tseries/offsets/test_business_hour.py

@@ -231,8 +231,9 @@ def test_add_datetime(
         assert offset8 + dt == datetime(2014, 7, 1, 11)
         assert offset9 + dt == datetime(2014, 7, 1, 22)
         assert offset10 + dt == datetime(2014, 7, 1, 1)
+        assert dt + 0 * offset1 == dt
 
-    def test_sub(self, dt, offset2, _offset):
+    def test_sub(self, dt, offset1, offset2, _offset):
         off = offset2
         msg = "Cannot subtract datetime from offset"
         with pytest.raises(TypeError, match=msg):
@@ -241,6 +242,8 @@ def test_sub(self, dt, offset2, _offset):
 
         assert dt - offset2 == dt + _offset(-3)
 
+        assert dt - 0 * offset1 == dt
+
     def testRollback1(
         self,
         dt,
@@ -972,6 +975,10 @@ def test_datetimeindex(self):
         for idx in [idx1, idx2, idx3]:
             tm.assert_index_equal(idx, expected)
 
+        idx4 = date_range(start="2014-07-01 10:00", freq="BH", periods=1)
+        expected4 = DatetimeIndex(["2014-07-01 10:00"], freq="BH")
+        tm.assert_index_equal(idx4, expected4)
+
     def test_bday_ignores_timedeltas(self):
         idx = date_range("2010/02/01", "2010/02/10", freq="12H")
         t1 = idx + BDay(offset=Timedelta(3, unit="H"))