add translate function for converting time zones.

Author: Marvin Kastner

pandas/core/indexes/datetimes.py

@@ -1276,52 +1276,64 @@ def _parsed_string_to_bounds(self, reso, parsed):
         else:
             target_tz = parsed.tzinfo
 
+        def translate(timestamp_lower, timestamp_upper):
+            if target_tz == self.tz:
+                return timestamp_lower, timestamp_upper
+            else:
+                return (
+                    timestamp_lower.tz_convert(self.tz),
+                    timestamp_upper.tz_convert(self.tz)
+                )
+
         if reso == 'year':
-            return (Timestamp(datetime(parsed.year, 1, 1), tz=target_tz),
+            return translate(Timestamp(datetime(parsed.year, 1, 1), tz=target_tz),
                     Timestamp(datetime(parsed.year, 12, 31, 23,
                                        59, 59, 999999), tz=target_tz))
         elif reso == 'month':
             d = libts.monthrange(parsed.year, parsed.month)[1]
-            return (Timestamp(datetime(parsed.year, parsed.month, 1),
+            return translate(Timestamp(datetime(parsed.year, parsed.month, 1),
                               tz=target_tz),
                     Timestamp(datetime(parsed.year, parsed.month, d, 23,
                                        59, 59, 999999), target_tz))
         elif reso == 'quarter':
             qe = (((parsed.month - 1) + 2) % 12) + 1  # two months ahead
             d = libts.monthrange(parsed.year, qe)[1]   # at end of month
-            return (Timestamp(datetime(parsed.year, parsed.month, 1),
+            return translate(Timestamp(datetime(parsed.year, parsed.month, 1),
                               tz=target_tz),
                     Timestamp(datetime(parsed.year, qe, d, 23, 59,
                                        59, 999999), tz=target_tz))
         elif reso == 'day':
             st = datetime(parsed.year, parsed.month, parsed.day)
-            return (Timestamp(st, tz=target_tz),
+            return translate(Timestamp(st, tz=target_tz),
                     Timestamp(Timestamp(st + offsets.Day(),
                                         tz=target_tz).value - 1))
         elif reso == 'hour':
             st = datetime(parsed.year, parsed.month, parsed.day,
                           hour=parsed.hour)
-            return (Timestamp(st, tz=target_tz),
+            return translate(Timestamp(st, tz=target_tz),
                     Timestamp(Timestamp(st + offsets.Hour(),
                                         tz=target_tz).value - 1))
         elif reso == 'minute':
             st = datetime(parsed.year, parsed.month, parsed.day,
                           hour=parsed.hour, minute=parsed.minute)
-            return (Timestamp(st, tz=target_tz),
+            return translate(Timestamp(st, tz=target_tz),
                     Timestamp(Timestamp(st + offsets.Minute(),
                                         tz=target_tz).value - 1))
         elif reso == 'second':
             st = datetime(parsed.year, parsed.month, parsed.day,
                           hour=parsed.hour, minute=parsed.minute,
                           second=parsed.second)
-            return (Timestamp(st, tz=target_tz),
+            return translate(Timestamp(st, tz=target_tz),
                     Timestamp(Timestamp(st + offsets.Second(),
                                         tz=target_tz).value - 1))
         elif reso == 'microsecond':
             st = datetime(parsed.year, parsed.month, parsed.day,
                           parsed.hour, parsed.minute, parsed.second,
                           parsed.microsecond)
-            return (Timestamp(st, tz=target_tz), Timestamp(st, tz=target_tz))
+            return translate(
+                Timestamp(st, tz=target_tz),
+                Timestamp(st, tz=target_tz)
+            )
         else:
             raise KeyError