diff --git a/qt_helpers.cpp b/qt_helpers.cpp
index 62def121b..3f41d0f87 100644
--- a/qt_helpers.cpp
+++ b/qt_helpers.cpp
@@ -5,6 +5,7 @@
 #include <QWidget>
 #include <QStyle>
 #include <QVariant>
+#include <QDateTime>
 
 QString font_as_stylesheet (QFont const& font)
 {
@@ -35,3 +36,15 @@ void update_dynamic_property (QWidget * widget, char const * property, QVariant
   widget->style ()->polish (widget);
   widget->update ();
 }
+
+QDateTime qt_round_date_time_to (QDateTime dt, int seconds)
+{
+  dt.setSecsSinceEpoch (dt.addSecs (seconds - 1).toSecsSinceEpoch () / seconds * seconds);
+  return dt;
+}
+
+QDateTime qt_truncate_date_time_to (QDateTime dt, int seconds)
+{
+  dt.setSecsSinceEpoch (dt.toSecsSinceEpoch () / seconds * seconds);
+  return dt;
+}
diff --git a/qt_helpers.hpp b/qt_helpers.hpp
index 33f501437..638c50e2a 100644
--- a/qt_helpers.hpp
+++ b/qt_helpers.hpp
@@ -69,6 +69,12 @@ QString font_as_stylesheet (QFont const&);
 // conditional style sheet updates
 void update_dynamic_property (QWidget *, char const * property, QVariant const& value);
 
+// round a QDateTime instance to an interval
+QDateTime qt_round_date_time_to (QDateTime dt, int seconds);
+
+// truncate a QDateTime to an interval
+QDateTime qt_truncate_date_time_to (QDateTime dt, int seconds);
+
 template <class T>
 class VPtr
 {