OSB-28: change dateformat string

LCU/Maintenance/DBInterface/monitoringdb/views/controllers.py

@@ -515,13 +515,13 @@ result:
                 annotate(n_errors=Count('observation__station__name'))
 
         errors_per_station_in_bin = dict()
-
+        central_time_str = central_time.strftime('%Y-%m-%d')
         if test_type in ['S', 'B']:
             for result in station_test_results:
                 station_name = result['station_test__station__name']
                 errors_per_station_in_bin[station_name] = dict(station_name=station_name,
                                                                n_errors=result['n_errors'],
-                                                               time=central_time)
+                                                               time=central_time_str)
 
         if test_type in ['R', 'B']:
             for result in rtsm_results:
@@ -529,7 +529,7 @@ result:
                 if station_name not in errors_per_station_in_bin:
                     errors_per_station_in_bin[station_name] = dict(station_name=station_name,
                                                                    n_errors=result['n_errors'],
-                                                                   time=central_time)
+                                                                   time=central_time_str)
                 else:
                     errors_per_station_in_bin[station_name]['n_errors'] += result['n_errors']