BUG: Correctly weekly resample over DST

doc/source/whatsnew/v0.24.0.txt

@@ -691,6 +691,7 @@ Timezones
 - Bug in :meth:`DatetimeIndex.unique` that did not re-localize tz-aware dates correctly (:issue:`21737`)
 - Bug when indexing a :class:`Series` with a DST transition (:issue:`21846`)
 - Bug in :meth:`DataFrame.resample` and :meth:`Series.resample` where an ``AmbiguousTimeError`` or ``NonExistentTimeError`` would raise if a timezone aware timeseries ended on a DST transition (:issue:`19375`, :issue:`10117`)
+- Bug in :meth:`DataFrame.resample` and :meth:`Series.resample` when resampling by a weekly offset (``'W'``) across a DST transition (:issue:`9119`, :issue:`21459`)
 
 Offsets
 ^^^^^^^

pandas/core/resample.py

@@ -16,7 +16,8 @@
 from pandas.tseries.frequencies import to_offset, is_subperiod, is_superperiod
 from pandas.core.indexes.datetimes import DatetimeIndex, date_range
 from pandas.core.indexes.timedeltas import TimedeltaIndex
-from pandas.tseries.offsets import DateOffset, Tick, Day, delta_to_nanoseconds
+from pandas.tseries.offsets import (DateOffset, Tick, Day,
+                                    delta_to_nanoseconds, Nano)
 from pandas.core.indexes.period import PeriodIndex
 from pandas.errors import AbstractMethodError
 import pandas.core.algorithms as algos
@@ -1395,18 +1396,21 @@ def _get_time_bins(self, ax):
     def _adjust_bin_edges(self, binner, ax_values):
         # Some hacks for > daily data, see #1471, #1458, #1483
 
-        bin_edges = binner.asi8
-
         if self.freq != 'D' and is_superperiod(self.freq, 'D'):
-            day_nanos = delta_to_nanoseconds(timedelta(1))
             if self.closed == 'right':
-                bin_edges = bin_edges + day_nanos - 1
+                # GH 21459, GH 9119: Adjust the bins relative to the wall time
+                bin_edges = binner.tz_localize(None)
+                bin_edges = bin_edges + timedelta(1) - Nano(1)
+                bin_edges = bin_edges.tz_localize(binner.tz).asi8
+            else:
+                bin_edges = binner.asi8
 
             # intraday values on last day
             if bin_edges[-2] > ax_values.max():
                 bin_edges = bin_edges[:-1]
                 binner = binner[:-1]
-
+        else:
+            bin_edges = binner.asi8
         return binner, bin_edges
 
     def _get_time_delta_bins(self, ax):

pandas/tests/test_resample.py

@@ -2114,6 +2114,28 @@ def test_downsample_across_dst(self):
                                            freq='H'))
         tm.assert_series_equal(result, expected)
 
+    def test_downsample_across_dst_weekly(self):
+        # GH 9119, GH 21459
+        df = DataFrame(index=DatetimeIndex([
+            '2017-03-25', '2017-03-26', '2017-03-27',
+            '2017-03-28', '2017-03-29'
+        ], tz='Europe/Amsterdam'),
+            data=[11, 12, 13, 14, 15])
+        result = df.resample('1W').sum()
+        expected = DataFrame([23, 42], index=pd.DatetimeIndex([
+            '2017-03-26', '2017-04-02'
+        ], tz='Europe/Amsterdam'))
+        tm.assert_frame_equal(result, expected)
+
+        idx = pd.date_range("2013-04-01", "2013-05-01", tz='Europe/London',
+                            freq='H')
+        s = Series(index=idx)
+        result = s.resample('W').mean()
+        expected = Series(index=pd.date_range(
+            '2013-04-07', freq='W', periods=5, tz='Europe/London'
+        ))
+        tm.assert_series_equal(result, expected)
+
     def test_resample_with_nat(self):
         # GH 13020
         index = DatetimeIndex([pd.NaT,