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-utils.c

@@ -110,8 +110,7 @@ datetime_to_icaltime (GDateTime *dt)
 }
 
 GDateTime*
-icaltime_to_datetime (const icaltimetype  *date,
-                      GTimeZone          **timezone)
+icaltime_to_datetime (const icaltimetype  *date)
 {
   GDateTime *dt;
   GTimeZone *tz;
@@ -125,10 +124,7 @@ icaltime_to_datetime (const icaltimetype  *date,
                         date->is_date ? 0 : date->minute,
                         date->is_date ? 0 : date->second);
 
-  if (timezone)
-    *timezone = tz;
-  else
-    g_clear_pointer (&tz, g_time_zone_unref);
+  g_clear_pointer (&tz, g_time_zone_unref);
 
   return dt;
 }
@@ -427,15 +423,11 @@ build_component_from_details (const gchar        *summary,
   ECalComponent *event;
   ECalComponentDateTime dt;
   ECalComponentText summ;
-  GTimeZone *tz;
-
-  tz = g_time_zone_new_local ();
 
   event = e_cal_component_new ();
   e_cal_component_set_new_vtype (event, E_CAL_COMPONENT_EVENT);
 
   dt.value = (icaltimetype*) initial_date;
-  dt.tzid = g_time_zone_get_abbreviation (tz, 0);
   e_cal_component_set_dtstart (event, &dt);
 
   if (final_date != NULL)
@@ -458,8 +450,6 @@ build_component_from_details (const gchar        *summary,
 
   e_cal_component_commit_sequence (event);
 
-  g_clear_pointer (&tz, g_time_zone_unref);
-
   return event;
 }
 
@@ -785,3 +775,24 @@ get_source_parent_name_color (GcalManager  *manager,
       *color = gdk_rgba_to_string (&c);
     }
 }
+
+gchar*
+format_utc_offset (gint offset)
+{
+  const char *sign = "+";
+  gint hours, minutes, seconds;
+
+  if (offset < 0) {
+      offset = -offset;
+      sign = "-";
+  }
+
+  hours = offset / 3600;
+  minutes = (offset % 3600) / 60;
+  seconds = offset % 60;
+
+  if (seconds > 0)
+    return g_strdup_printf ("%s%02i%02i%02i", sign, hours, minutes, seconds);
+  else
+    return g_strdup_printf ("%s%02i%02i", sign, hours, minutes);
+}