diff --git a/src/CLI.cpp b/src/CLI.cpp
index f1215309..7921b086 100644
--- a/src/CLI.cpp
+++ b/src/CLI.cpp
@@ -34,6 +34,7 @@
 #include <sstream>
 #include <algorithm>
 #include <set>
+#include <Duration.h>
 
 ////////////////////////////////////////////////////////////////////////////////
 A2::A2 (const std::string& raw, Lexer::Type lextype)
@@ -589,3 +590,19 @@ std::string CLI::getAnnotation () const
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+Duration CLI::getDuration () const
+{
+  std::string delta;
+  for (auto& arg : _args)
+  {
+    if (arg.hasTag ("FILTER") &&
+        arg._lextype == Lexer::Type::duration)
+    {
+      delta = arg.attribute ("raw");
+    }
+  }
+  Duration dur (delta);
+  return dur;
+}
+
+////////////////////////////////////////////////////////////////////////////////
diff --git a/src/CLI.h b/src/CLI.h
index d75691da..f097ecb3 100644
--- a/src/CLI.h
+++ b/src/CLI.h
@@ -32,6 +32,7 @@
 #include <set>
 #include <vector>
 #include <map>
+#include <Duration.h>
 
 // Represents a single argument.
 class A2
@@ -68,6 +69,7 @@ public:
   std::set <int> getIds () const;
   std::vector<std::string> getTags () const;
   std::string getAnnotation() const;
+  Duration getDuration() const;
   std::string dump (const std::string& title = "CLI Parser") const;
 
 private:
@@ -86,4 +88,3 @@ public:
 };
 
 #endif
-
diff --git a/src/commands/CmdLengthen.cpp b/src/commands/CmdLengthen.cpp
index 9cff566e..3391c638 100644
--- a/src/commands/CmdLengthen.cpp
+++ b/src/commands/CmdLengthen.cpp
@@ -49,16 +49,7 @@ int CmdLengthen (
     throw std::string ("IDs must be specified. See 'timew help lengthen'.");
   }
 
-  std::string delta;
-
-  for (auto& arg : cli._args)
-  {
-    if (arg.hasTag ("FILTER") &&
-        arg._lextype == Lexer::Type::duration)
-    {
-      delta = arg.attribute ("raw");
-    }
-  }
+  Duration dur = cli.getDuration ();
 
   journal.startTransaction ();
 
@@ -75,7 +66,6 @@ int CmdLengthen (
 
     database.deleteInterval (interval);
 
-    Duration dur (delta);
     interval.end += dur.toTime_t ();
     validate (cli, rules, database, interval);
     database.addInterval (interval, verbose);
diff --git a/src/commands/CmdResize.cpp b/src/commands/CmdResize.cpp
index 3dda1849..23da05f8 100644
--- a/src/commands/CmdResize.cpp
+++ b/src/commands/CmdResize.cpp
@@ -48,15 +48,7 @@ int CmdResize (
     throw std::string ("IDs must be specified. See 'timew help resize'.");
   }
 
-  std::string delta;
-  for (auto& arg : cli._args)
-  {
-    if (arg.hasTag ("FILTER") &&
-        arg._lextype == Lexer::Type::duration)
-    {
-      delta = arg.attribute ("raw");
-    }
-  }
+  Duration dur = cli.getDuration ();
 
   journal.startTransaction ();
 
@@ -70,7 +62,6 @@ int CmdResize (
       throw format ("Cannot resize open interval @{1}", interval.id);
     }
 
-    Duration dur (delta);
     database.deleteInterval (interval);
 
     interval.end = interval.start + dur.toTime_t ();
diff --git a/src/commands/CmdShorten.cpp b/src/commands/CmdShorten.cpp
index 3eac5459..379cf174 100644
--- a/src/commands/CmdShorten.cpp
+++ b/src/commands/CmdShorten.cpp
@@ -48,15 +48,7 @@ int CmdShorten (
     throw std::string ("IDs must be specified. See 'timew help shorten'.");
   }
 
-  std::string delta;
-  for (auto& arg : cli._args)
-  {
-    if (arg.hasTag ("FILTER") &&
-        arg._lextype == Lexer::Type::duration)
-    {
-      delta = arg.attribute ("raw");
-    }
-  }
+  Duration dur = cli.getDuration ();
 
   journal.startTransaction ();
 
@@ -71,7 +63,6 @@ int CmdShorten (
       throw format ("Cannot shorten open interval @{1}", interval.id);
     }
 
-    Duration dur (delta);
     if (dur > (interval.end - interval.start))
     {
       throw format ("Cannot shorten interval @{1} by {2} because it is only {3} in length.",