Fix Activity Start Time Precision (#45175)

diff --git a/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs b/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs
index 50823c0..3835119 100644 (file)
--- a/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs
+++ b/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs
@@ -1017,7 +1017,7 @@ namespace System.Diagnostics
                 }
             }
 
-            activity.StartTimeUtc = startTime == default ? DateTime.UtcNow : startTime.UtcDateTime;
+            activity.StartTimeUtc = startTime == default ? GetUtcNow() : startTime.UtcDateTime;
 
             activity.IsAllDataRequested = request == ActivitySamplingResult.AllData || request == ActivitySamplingResult.AllDataAndRecorded;