fix timestamp shift

pts/feature/transform.py

@@ -17,12 +17,9 @@ MAX_IDLE_TRANSFORMS = 100
 def shift_timestamp(ts: pd.Timestamp, offset: int) -> pd.Timestamp:
     try:
         # this line looks innocent, but can create a date which is out of
-        # bounds values over year 9999 raise a ValueError
+        # bounds. Values over year 9999 raise a ValueError and
         # values over 2262-04-11 raise a pandas OutOfBoundsDatetime
-        result = ts + offset * ts.freq
-        # For freq M and W pandas seems to lose the freq of the timestamp,
-        # so we explicitly set it.
-        return pd.Timestamp(result, freq=ts.freq)
+        return ts + offset * ts.freq
     except (ValueError, pd._libs.OutOfBoundsDatetime) as ex:
         raise Exception(ex)