diff --git a/src/Timeline.cpp b/src/Timeline.cpp
index 9098c482..473fce3c 100644
--- a/src/Timeline.cpp
+++ b/src/Timeline.cpp
@@ -109,9 +109,9 @@ std::vector <Interval> Timeline::tracked (Rules& rules) const
 
 ////////////////////////////////////////////////////////////////////////////////
 // Untracked time is that which is not excluded, and not filled. Gaps.
-std::vector <Interval> Timeline::untracked (Rules& rules) const
+std::vector <Range> Timeline::untracked (Rules& rules) const
 {
-  std::vector <Interval> gaps;
+  std::vector <Range> gaps;
 
   // Get the set of expanded exclusions that overlap the range defined by the
   // timeline. If no range is defined, derive it from the set of all data.
diff --git a/src/Timeline.h b/src/Timeline.h
index 5d510011..5b7b4338 100644
--- a/src/Timeline.h
+++ b/src/Timeline.h
@@ -40,7 +40,7 @@ public:
   void include (const Interval&);
   void exclude (const Exclusion&);
   std::vector <Interval> tracked (Rules&) const;
-  std::vector <Interval> untracked (Rules&) const;
+  std::vector <Range> untracked (Rules&) const;
   std::vector <Range> excluded (Rules&) const;
   std::string dump () const;
 
diff --git a/src/commands/CmdGaps.cpp b/src/commands/CmdGaps.cpp
index 6464b58b..9bcac434 100644
--- a/src/commands/CmdGaps.cpp
+++ b/src/commands/CmdGaps.cpp
@@ -25,21 +25,22 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include <cmake.h>
+#include <commands.h>
+#include <timew.h>
 #include <iostream>
 
 ////////////////////////////////////////////////////////////////////////////////
-int CmdGaps ()
+int CmdGaps (
+  const CLI& cli,
+  Rules& rules,
+  Database& database)
 {
-  std::cout << "[gaps: shows untracked gaps in the current day/week/month]\n";
-
-  // TODO If there are no exclusions defineѕ.
-  //   TODO Error
-
-  // TODO Load all data.
-  // TODO Apply filter.
-  // TODO Invert the union exclusions and incluѕions
-  // TODO For each interval
-  // TODO   Display
+  auto filter = createFilterIntervalFromCLI (cli);
+  auto timeline = createTimelineFromData (rules, database, filter);
+  for (auto& gap : timeline.untracked (rules))
+  {
+    std::cout << "# gap " << gap.dump () << "\n";
+  }
 
   return 0;
 }
diff --git a/src/commands/commands.h b/src/commands/commands.h
index 2f1d4b6a..d2d8091e 100644
--- a/src/commands/commands.h
+++ b/src/commands/commands.h
@@ -39,7 +39,7 @@ int CmdDefault       (            Rules&, Database&                   );
 int CmdDiagnostics   (            Rules&, Database&, const Extensions&);
 int CmdExport        (const CLI&, Rules&, Database&                   );
 int CmdExtensions    (            Rules&,            const Extensions&);
-int CmdGaps          (                                                );
+int CmdGaps          (const CLI&, Rules&, Database&                   );
 int CmdHelpUsage     (                                                );
 int CmdHelp          (const CLI&                                      );
 int CmdImport        (                                                );
diff --git a/src/init.cpp b/src/init.cpp
index f78b2809..6a809d5d 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -227,7 +227,7 @@ int dispatchCommand (
     else if (command == "diagnostics") status = CmdDiagnostics   (     rules, database, extensions);
     else if (command == "export")      status = CmdExport        (cli, rules, database            );
     else if (command == "extensions")  status = CmdExtensions    (     rules,           extensions);
-    else if (command == "gaps")        status = CmdGaps          (                                );
+    else if (command == "gaps")        status = CmdGaps          (cli, rules, database            );
     else if (command == "help")        status = CmdHelp          (cli                             );
     else if (command == "import")      status = CmdImport        (                                );
     else if (command == "report")      status = CmdReport        (cli, rules, database, extensions);