event: fix timezone handling

Using libical with libecal means that the dates
are always stored as UTF dates, and we receive the
timezone as the ECalComponentDateTime::tzid value.

This fact was net being considered when adding date
support on GcalEvent, and was causing various issues
when displaying dates.

Fix that by properly handling timezones in GcalEvent.

src/gcal-month-view.c

@@ -488,6 +488,8 @@ rebuild_popover_for_day (GcalMonthView *view,
   PangoFontDescription *ofont_desc;
   gint font_height, padding_bottom;
 
+  GTimeZone *tz;
+
   priv = gcal_month_view_get_instance_private (view);
   ppriv = GCAL_SUBSCRIBER_VIEW (view)->priv;
 
@@ -499,6 +501,7 @@ rebuild_popover_for_day (GcalMonthView *view,
   gtk_container_foreach (GTK_CONTAINER (priv->events_list_box), (GtkCallback) gtk_widget_destroy, NULL);
 
   l = g_hash_table_lookup (ppriv->overflow_cells, GINT_TO_POINTER (priv->pressed_overflow_indicator));
+  tz = g_time_zone_new_local ();
 
   /* Setup the start & end dates of the events as the begin & end of day */
   if (l != NULL)
@@ -506,9 +509,7 @@ rebuild_popover_for_day (GcalMonthView *view,
       GDateTime *current_date;
       GDateTime *dt_start;
       GDateTime *dt_end;
-      GTimeZone *tz;
-
-      current_date = icaltime_to_datetime (priv->date, &tz);
+      current_date = icaltime_to_datetime (priv->date);
       dt_start = g_date_time_new (tz,
                                   g_date_time_get_year (current_date),
                                   g_date_time_get_month (current_date),
@@ -536,9 +537,10 @@ rebuild_popover_for_day (GcalMonthView *view,
       g_clear_pointer (&current_date, g_date_time_unref);
       g_clear_pointer (&dt_start, g_date_time_unref);
       g_clear_pointer (&dt_end, g_date_time_unref);
-      g_clear_pointer (&tz, g_time_zone_unref);
     }
 
+  g_clear_pointer (&tz, g_time_zone_unref);
+
   /* placement calculation */
   start_grid_y = get_start_grid_y (GTK_WIDGET (view));
   shown_rows = ceil ((priv->days_delay + icaltime_days_in_month (priv->date->month, priv->date->year)) / 7.0);