diff --git a/src/Duration.cpp b/src/Duration.cpp
index 458f89e34..18c77c06c 100644
--- a/src/Duration.cpp
+++ b/src/Duration.cpp
@@ -452,3 +452,14 @@ void Duration::parse (const std::string& input)
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+const std::vector <std::string> Duration::get_units ()
+{
+  std::vector <std::string> units;
+  for (unsigned int i = 0; i < NUM_DURATIONS; ++i)
+    if (strcmp (durations[i], "-"))
+      units.push_back (durations[i]);
+
+  return units;
+}
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/Duration.h b/src/Duration.h
index 065135bac..f4e57b6a2 100644
--- a/src/Duration.h
+++ b/src/Duration.h
@@ -28,6 +28,7 @@
 #define INCLUDED_DURATION
 #define L10N                                           // Localization complete.
 
+#include <vector>
 #include <string>
 #include <time.h>
 
@@ -59,6 +60,8 @@ public:
   static bool valid (const std::string&);
   void parse (const std::string&);
 
+  static const std::vector <std::string> get_units ();
+
 protected:
   time_t mSecs;
   bool mNegative;