BUG: error calculating BusinessHourMixin.apply for long business hour per day (#26381)

* BUG: error calculating BusinessHourMixin.apply for long business hour per day

Author: jiangyue12392

doc/source/whatsnew/v0.25.0.rst

@@ -319,7 +319,7 @@ Timedelta
 
 - Bug in :func:`TimedeltaIndex.intersection` where for non-monotonic indices in some cases an empty ``Index`` was returned when in fact an intersection existed (:issue:`25913`)
 - Bug with comparisons between :class:`Timedelta` and ``NaT`` raising ``TypeError`` (:issue:`26039`)
--
+- Bug when adding or subtracting a :class:`BusinessHour` to a :class:`Timestamp` with the resulting time landing in a following or prior day respectively (:issue:`26381`)
 
 Timezones
 ^^^^^^^^^

pandas/tests/tseries/offsets/test_offsets.py

@@ -1287,6 +1287,23 @@ def test_opening_time(self, case):
         datetime(2014, 7, 7, 19, 30): datetime(2014, 7, 5, 4, 30),
         datetime(2014, 7, 7, 19, 30, 30): datetime(2014, 7, 5, 4, 30, 30)}))
 
+    # long business hours (see gh-26381)
+    apply_cases.append((BusinessHour(n=4, start='00:00', end='23:00'), {
+        datetime(2014, 7, 3, 22): datetime(2014, 7, 4, 3),
+        datetime(2014, 7, 4, 22): datetime(2014, 7, 7, 3),
+        datetime(2014, 7, 3, 22, 30): datetime(2014, 7, 4, 3, 30),
+        datetime(2014, 7, 3, 22, 20): datetime(2014, 7, 4, 3, 20),
+        datetime(2014, 7, 4, 22, 30, 30): datetime(2014, 7, 7, 3, 30, 30),
+        datetime(2014, 7, 4, 22, 30, 20): datetime(2014, 7, 7, 3, 30, 20)}))
+
+    apply_cases.append((BusinessHour(n=-4, start='00:00', end='23:00'), {
+        datetime(2014, 7, 4, 3): datetime(2014, 7, 3, 22),
+        datetime(2014, 7, 7, 3): datetime(2014, 7, 4, 22),
+        datetime(2014, 7, 4, 3, 30): datetime(2014, 7, 3, 22, 30),
+        datetime(2014, 7, 4, 3, 20): datetime(2014, 7, 3, 22, 20),
+        datetime(2014, 7, 7, 3, 30, 30): datetime(2014, 7, 4, 22, 30, 30),
+        datetime(2014, 7, 7, 3, 30, 20): datetime(2014, 7, 4, 22, 30, 20)}))
+
     @pytest.mark.parametrize('case', apply_cases)
     def test_apply(self, case):
         offset, cases = case

pandas/tseries/offsets.py

@@ -689,7 +689,6 @@ def rollforward(self, dt):
 
     @apply_wraps
     def apply(self, other):
-        daytime = self._get_daytime_flag
         businesshours = self._get_business_hours_by_sec
         bhdelta = timedelta(seconds=businesshours)
 
@@ -731,21 +730,19 @@ def apply(self, other):
             result = other + timedelta(hours=hours, minutes=minutes)
 
             # because of previous adjustment, time will be larger than start
-            if ((daytime and (result.time() < self.start or
-                              self.end < result.time())) or
-                    not daytime and (self.end < result.time() < self.start)):
-                if n >= 0:
-                    bday_edge = self._prev_opening_time(other)
-                    bday_edge = bday_edge + bhdelta
-                    # calculate remainder
+            if n >= 0:
+                bday_edge = self._prev_opening_time(other) + bhdelta
+                if bday_edge < result:
                     bday_remain = result - bday_edge
                     result = self._next_opening_time(other)
                     result += bday_remain
-                else:
-                    bday_edge = self._next_opening_time(other)
+            else:
+                bday_edge = self._next_opening_time(other)
+                if bday_edge > result:
                     bday_remain = result - bday_edge
                     result = self._next_opening_time(result) + bhdelta
                     result += bday_remain
+
             # edge handling
             if n >= 0:
                 if result.time() == self.end: