fix ForecastModel.get_data handling of timezones (pvlib#1285)

* fix ForecastModel.get_data handling of timezones

* update pr number

Author: wholmgren

docs/sphinx/source/whatsnew/v0.9.0.rst

@@ -127,7 +127,7 @@ Enhancements
   for retrieving and reading BSRN solar radiation data files.
   (:pull:`1254`, :pull:`1145`, :issue:`1015`)
 * Add :func:`~pvlib.iotools.get_cams`,
-  :func:`~pvlib.iotools.parse_cams`, and 
+  :func:`~pvlib.iotools.parse_cams`, and
   :func:`~pvlib.iotools.read_cams`
   for retrieving, parsing, and reading CAMS Radiation and McClear time-series
   files. (:pull:`1175`)
@@ -179,9 +179,9 @@ Enhancements
 Bug fixes
 ~~~~~~~~~
 * Corrected an error in :py:func:`~pvlib.irradiance.perez` where the horizon
-  irradiance component was prevented from taking negative values. Negative 
-  values are intentional according to the original publication. Changes in 
-  output are expected to be small and primarily occur at low irradiance 
+  irradiance component was prevented from taking negative values. Negative
+  values are intentional according to the original publication. Changes in
+  output are expected to be small and primarily occur at low irradiance
   conditions.
   (:issue:`1238`, :pull:`1239`)
 * Pass weather data to solar position calculations in
@@ -205,7 +205,9 @@ Bug fixes
 * Changed deprecated use of ``.astype()`` to ``.view()`` in :py:mod:`~pvlib.solarposition`.
   (:pull:`1256`, :issue:`1261`, :pull:`1262`)
 * Fix :py:func:`~pvlib.tracking.singleaxis` AOI wrong when sun behind module.
-  (:pull:`1273`, :issue:`1221`) 
+  (:pull:`1273`, :issue:`1221`)
+* Fix :py:meth:`~pvlib.forecast.ForecastModel.get_data` failure to correct for
+  non-UTC timezones. (:issue:`1237`, :pull:`1285`)
 
 Testing
 ~~~~~~~

pvlib/forecast.py

@@ -183,7 +183,12 @@ def set_query_time_range(self, start, end):
         self.end = pd.Timestamp(end)
         if self.start.tz is None or self.end.tz is None:
             raise TypeError('start and end must be tz-localized')
-        self.query.time_range(self.start, self.end)
+        # don't assume that siphon or the server can handle anything other
+        # than UTC
+        self.query.time_range(
+            self.start.tz_convert('UTC'),
+            self.end.tz_convert('UTC')
+        )
 
     def set_query_latlon(self):
         '''
@@ -412,10 +417,14 @@ def set_time(self, time):
         -------
         pandas.DatetimeIndex
         '''
+        # np.masked_array with elements like real_datetime(2021, 8, 17, 16, 0)
+        # and dtype=object
         times = num2date(time[:].squeeze(), time.units,
                          only_use_cftime_datetimes=False,
                          only_use_python_datetimes=True)
-        self.time = pd.DatetimeIndex(pd.Series(times), tz=self.location.tz)
+        # convert to pandas, localize to UTC, convert to desired timezone
+        self.time = pd.DatetimeIndex(
+            times, tz='UTC').tz_convert(self.location.tz)
 
     def cloud_cover_to_ghi_linear(self, cloud_cover, ghi_clear, offset=35,
                                   **kwargs):