Merge branch 'master' of https://github.com/pandas-dev/pandas into ref-mgr-reduce

Author: jbrockmendel

README.md

@@ -32,7 +32,7 @@ its way towards this goal.
 Here are just a few of the things that pandas does well:
 
   - Easy handling of [**missing data**][missing-data] (represented as
-    `NaN`) in floating point as well as non-floating point data
+    `NaN`, `NA`, or `NaT`) in floating point as well as non-floating point data
   - Size mutability: columns can be [**inserted and
     deleted**][insertion-deletion] from DataFrame and higher dimensional
     objects

pandas/_libs/tslibs/offsets.pyx

@@ -3705,7 +3705,7 @@ cdef inline void _shift_months(const int64_t[:] dtindex,
     """See shift_months.__doc__"""
     cdef:
         Py_ssize_t i
-        int months_to_roll, compare_day
+        int months_to_roll
         npy_datetimestruct dts
 
     for i in range(count):
@@ -3715,10 +3715,8 @@ cdef inline void _shift_months(const int64_t[:] dtindex,
 
         dt64_to_dtstruct(dtindex[i], &dts)
         months_to_roll = months
-        compare_day = get_day_of_month(&dts, day_opt)
 
-        months_to_roll = roll_convention(dts.day, months_to_roll,
-                                         compare_day)
+        months_to_roll = _roll_qtrday(&dts, months_to_roll, 0, day_opt)
 
         dts.year = year_add_months(dts, months_to_roll)
         dts.month = month_add_months(dts, months_to_roll)