provide the timezone so that the UI doesn't have to

this will also ensure that UI doesn't use a different front end library
that will yield different results than the underlying Python code

awx/api/serializers.py

@@ -4511,9 +4511,14 @@ class SchedulePreviewSerializer(BaseSerializer):
 class ScheduleSerializer(LaunchConfigurationBaseSerializer, SchedulePreviewSerializer):
     show_capabilities = ['edit', 'delete']
 
+    timezone = serializers.SerializerMethodField()
+
     class Meta:
         model = Schedule
-        fields = ('*', 'unified_job_template', 'enabled', 'dtstart', 'dtend', 'rrule', 'next_run',)
+        fields = ('*', 'unified_job_template', 'enabled', 'dtstart', 'dtend', 'rrule', 'next_run', 'timezone',)
+
+    def get_timezone(self, obj):
+        return obj.timezone
 
     def get_related(self, obj):
         res = super(ScheduleSerializer, self).get_related(obj)

awx/api/views.py

@@ -745,11 +745,7 @@ class ScheduleZoneInfo(APIView):
     swagger_topic = 'System Configuration'
 
     def get(self, request):
-        from dateutil.zoneinfo import get_zonefile_instance
-        return Response([
-            {'name': zone}
-            for zone in sorted(get_zonefile_instance().zones)
-        ])
+        return Response(Schedule.get_zoneinfo())
 
 
 class LaunchConfigCredentialsBase(SubListAttachDetachAPIView):