diff --git a/Graphs/gSummaryChart.cpp b/Graphs/gSummaryChart.cpp
index 39212c89..75aa616d 100644
--- a/Graphs/gSummaryChart.cpp
+++ b/Graphs/gSummaryChart.cpp
@@ -498,6 +498,8 @@ QString formatTime(EventDataType v, bool show_seconds=false, bool duration=false
     if (show_12hr) {
         h>=12 ? pm[0]='p' : pm[0]='a'; // yes, inverted..
         h %= 12;
+        if (h==0) h=12;
+
     } else {
         pm[0]=0;
     }
diff --git a/Graphs/gYAxis.cpp b/Graphs/gYAxis.cpp
index 42159391..51fcc65d 100644
--- a/Graphs/gYAxis.cpp
+++ b/Graphs/gYAxis.cpp
@@ -264,6 +264,7 @@ const QString gYAxisTime::Format(EventDataType v, int dp)
     if (show_12hr) {
         h>=12 ? pm[0]='p' : pm[0]='a'; // yes, inverted..
         h %= 12;
+        if (h==0) h=12;
     } else {
         pm[0]=0;
     }