diff --git a/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs b/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
index 19157e5f..1faa769f 100644
--- a/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
+++ b/AsbCloudInfrastructure/Services/Subsystems/SubsystemOperationTimeService.cs
@@ -111,30 +111,31 @@ namespace AsbCloudInfrastructure.Services.Subsystems
 
         private static IEnumerable<SubsystemOperationTime> TrimOperation(IEnumerable<SubsystemOperationTime> data, DateTimeOffset? gtDate, DateTimeOffset? ltDate)
         {
-            if (!ltDate.HasValue && !gtDate.HasValue) return data;
+            if (!ltDate.HasValue && !gtDate.HasValue) 
+                return data.Select(d => d.Adapt<SubsystemOperationTime>());
 
             var items = data.Select((item) => 
             {
-                var dateDiff = (ltDate!.Value - gtDate!.Value).TotalSeconds;
-                var depthDiff = (item.DepthEnd  ?? 0) - (item.DepthStart ?? 0);
-                var a = depthDiff / (float)dateDiff;
-                var x = (float)(item.DateStart - gtDate.Value).TotalSeconds;
-                var b = item.DepthStart;
-                var cutDepth = a * x + b;
-
                 var operationTime = item.Adapt<SubsystemOperationTime>();
+                if (!(item.DepthStart.HasValue && item.DepthEnd.HasValue))
+                    return operationTime;
+
+                var dateDiff = (item.DateEnd - item.DateStart).TotalSeconds;
+                var depthDiff = item.DepthEnd.Value - item.DepthStart.Value;
+                var a = depthDiff / dateDiff;               
+                var b = item.DepthStart.Value;
 
                 if (gtDate.HasValue && item.DateStart < gtDate.Value)
                 {
                     operationTime.DateStart = gtDate.Value;
-                    operationTime.DepthStart = cutDepth;
+                    var x = (gtDate.Value - item.DateStart).TotalSeconds;
+                    operationTime.DepthStart = (float)(a * x + b);
                 }
                 if (ltDate.HasValue && item.DateEnd > ltDate.Value)
                 {
                     operationTime.DateEnd = ltDate.Value;
-                    operationTime.DepthEnd = cutDepth;
-
-                    var test = data;
+                    var x = (ltDate.Value - item.DateStart).TotalSeconds;
+                    operationTime.DepthEnd = (float)(a * x + b);
                 }
                 return operationTime;
             });