diff --git a/src/Exclusion.cpp b/src/Exclusion.cpp
index ff6c0e33..5560be49 100644
--- a/src/Exclusion.cpp
+++ b/src/Exclusion.cpp
@@ -56,13 +56,21 @@ void Exclusion::initialize (const std::string& line)
   {
     if (_tokens.size () == 4 &&
         _tokens[1] == "day"  &&
-        (_tokens[2] == "on" || _tokens[2] == "off"))
+        _tokens[2] == "on")
     {
+      _additive = true;
+      return;
+    }
+    if (_tokens.size () == 4 &&
+        _tokens[1] == "day"  &&
+        _tokens[2] == "off")
+    {
+      _additive = false;
       return;
     }
     else if (Datetime::dayOfWeek (_tokens[1]) != -1)
-             // TODO Check the time range args.
     {
+      _additive = false;
       return;
     }
   }
@@ -76,6 +84,36 @@ std::vector <std::string> Exclusion::tokens () const
   return _tokens;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Within range, yield a collection of recurring ranges as defined by _tokens.
+//   exc monday <block> [<block> ...]
+//   exc day on <date>
+//   exc day off <date>
+std::vector <Daterange> Exclusion::ranges (const Daterange& range) const
+{
+  std::vector <Daterange> results;
+
+  if (_tokens[1] == "day" &&
+      (_tokens[2] == "on" ||
+       _tokens[2] == "off"))
+  {
+    Datetime start (_tokens[3]);
+    Datetime end (start);
+    ++end;
+    Daterange day (start, end);
+    if (range.overlap (day))
+      results.push_back (day);
+  }
+
+  return results;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+bool Exclusion::additive () const
+{
+  return _additive;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 std::string Exclusion::serialize () const
 {
diff --git a/src/Exclusion.h b/src/Exclusion.h
index 8b8d64c1..e0833692 100644
--- a/src/Exclusion.h
+++ b/src/Exclusion.h
@@ -28,6 +28,7 @@
 #define INCLUDED_EXCLUSION
 
 #include <Interval.h>
+#include <Daterange.h>
 #include <vector>
 #include <string>
 
@@ -37,12 +38,15 @@ public:
   Exclusion () = default;
   void initialize (const std::string&);
   std::vector <std::string> tokens () const;
+  std::vector <Daterange> ranges (const Daterange&) const;
+  bool additive () const;
 
   std::string serialize () const;
   std::string dump () const;
 
 private:
-  std::vector <std::string> _tokens;
+  std::vector <std::string> _tokens   {};
+  bool                      _additive {false};
 };
 
 #endif