event: correctly interpret floating time events

When dealing with floating time events the timezone used was UTC,
but according to RFC5545 when the timezone is not specified the
local timezone should be used.

Fixes #171

src/core/gcal-event.c

@@ -201,11 +201,11 @@ get_timezone_from_ical (GcalEvent             *self,
     }
 
   /*
-   * If tz is NULL, the timezone identifier is invalid. Fallback to UTC
+   * If tz is NULL, the timezone identifier is invalid. Fallback to the local timezone
    * in this case.
    */
   if (!tz)
-    tz = g_time_zone_new_utc ();
+    tz = g_time_zone_new_local ();
 
   GCAL_TRACE_MSG ("%s (%p)", g_time_zone_get_identifier (tz), tz);