diff --git a/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs b/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
index 1faa769f..a971116e 100644
--- a/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
+++ b/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
@@ -230,11 +230,15 @@ namespace AsbCloudInfrastructure.Services.Subsystems
 
             var beginUTC = gtDate.HasValue
                 ? gtDate.Value.ToUtcDateTimeOffset(hoursOffset)
-                : DateTime.Today.AddDays(-1).ToUtcDateTimeOffset(hoursOffset);
+                : db.SubsystemOperationTimes.Min(s => s.DateStart)
+                    .DateTime
+                    .ToUtcDateTimeOffset(hoursOffset);
 
             var endUTC = ltDate.HasValue
                 ? ltDate.Value.ToUtcDateTimeOffset(hoursOffset)
-                : DateTime.Today.ToUtcDateTimeOffset(hoursOffset);
+                : db.SubsystemOperationTimes.Max(s => s.DateEnd)
+                    .DateTime
+                    .ToUtcDateTimeOffset(hoursOffset);
 
             var telemetryIds = wells
                 .Where(w => w.IdTelemetry is not null)