diff --git a/src/lib/test/test-helper.hpp b/src/lib/test/test-helper.hpp
index e124055b1..8a778840f 100644
--- a/src/lib/test/test-helper.hpp
+++ b/src/lib/test/test-helper.hpp
@@ -26,6 +26,7 @@
 
 
 #include "lib/symbol.hpp"
+#include "lib/time/timevalue.hpp"
 
 #include <typeinfo>
 #include <string>
@@ -102,10 +103,10 @@ namespace test{
   
     
   /** create a random but not insane Time value */    
-  inline Time
+  inline lib::time::Time
   randTime ()
   {
-    return Time (500 * (rand() % 2), (rand() % 600));
+    return lib::time::Time (500 * (rand() % 2), (rand() % 600));
   }
   
   /** create garbage string of given length
diff --git a/src/proc/asset/media.cpp b/src/proc/asset/media.cpp
index 53cd1f1fd..d67231e89 100644
--- a/src/proc/asset/media.cpp
+++ b/src/proc/asset/media.cpp
@@ -28,6 +28,7 @@
 #include "proc/asset/unknown.hpp"
 #include "proc/mobject/session/clip.hpp"
 #include "proc/mobject/session/mobjectfactory.hpp"
+#include "lib/time/timevalue.hpp"
 #include "lib/util.hpp"
 #include "include/logging.h"
 
@@ -36,6 +37,8 @@
 
 
 using util::isnil;
+using lib::time::FSecs;
+using lib::time::Duration;
 
 using boost::format;
 using boost::regex;
@@ -44,11 +47,10 @@ using boost::regex_search;
 using std::tr1::dynamic_pointer_cast;
 
 
-namespace asset
-  {
+namespace asset {
   
-  namespace // Implementation details
-  {
+  namespace { // Implementation details
+    
     /** helper: extract a name token out of a given path/filename
      *  @return sanitised token based on the name (minus extension),
      *          empty string if not the common filename pattern.
@@ -116,7 +118,7 @@ namespace asset
   }
   
   
-  lumiera::Time
+  Duration
   Media::getLength()  const
   {
      return len_;
@@ -157,7 +159,7 @@ namespace asset
         if (isnil (key.name)) key.name=extractName(file);
         TODO ("file exists?");
         TODO ("extract media file properties");
-        Time length(25);
+        Duration length(FSecs(5));
         TODO ("detecting and wiring multichannel compound media!");
         pM = new Media (key,file,length); 
       }
diff --git a/src/proc/asset/media.hpp b/src/proc/asset/media.hpp
index d3b2c9024..bdd37da18 100644
--- a/src/proc/asset/media.hpp
+++ b/src/proc/asset/media.hpp
@@ -39,6 +39,7 @@
 
 #include "proc/asset.hpp"
 #include "lib/factory.hpp"
+#include "lib/time/timevalue.hpp"
 #include "proc/mobject/mobject.hpp"
 #include "proc/mobject/session/clip.hpp"
 
@@ -52,7 +53,7 @@ namespace asset {
   class ProcPatt;
   
   using lumiera::P;
-  using lumiera::Time;
+  using lib::time::Duration;
   
   
   template<>
@@ -71,7 +72,7 @@ namespace asset {
   class Media : public Asset
     {
       string filename_;
-      const Time len_;
+      const Duration len_;
       
     public:
       typedef P<Media> PMedia;
@@ -105,11 +106,11 @@ namespace asset {
       PClipMO createClip ();
       
       /** @return the overall length of the media represented by this asset */ 
-      virtual Time getLength ()  const;
+      virtual Duration getLength ()  const;
       
       
     protected:
-      Media (const Asset::Ident& idi, const string& file, Time length) 
+      Media (const Asset::Ident& idi, const string& file, Duration length) 
         : Asset(idi), filename_(file), len_(length) {}
       friend class MediaFactory;
       
diff --git a/src/proc/asset/unknown.cpp b/src/proc/asset/unknown.cpp
index ca25adf74..f8d3b81f1 100644
--- a/src/proc/asset/unknown.cpp
+++ b/src/proc/asset/unknown.cpp
@@ -38,7 +38,7 @@ namespace asset {
    *  on using the Unknown::getOrg() function.
    *  @note we don't depend on the refered media...
    */
-  Unknown::Unknown (const Asset::Ident& idi, string name, Time length)
+  Unknown::Unknown (const Asset::Ident& idi, string name, Duration length)
     : Media (idi, name, length)
   {
     TODO ("implement some sensible behaviour for the »unknown media« placeholder...");
diff --git a/src/proc/asset/unknown.hpp b/src/proc/asset/unknown.hpp
index fa3f5a291..31f3df6b0 100644
--- a/src/proc/asset/unknown.hpp
+++ b/src/proc/asset/unknown.hpp
@@ -25,13 +25,16 @@
 #define ASSET_UNKNOWN_H
 
 #include "proc/asset/media.hpp"
+#include "lib/time/timevalue.hpp"
 
 
 
 namespace asset {
   
+  using lib::time::FSecs;
+  using lib::time::Duration;
   
-  const lumiera::Time DUMMY_TIME (25); ///< @todo solve config management
+  const Duration DUMMY_TIME (FSecs(5)); ///< @todo solve config management
   
   /**
    * Placeholder Asset for unknown or unavailable media source.
@@ -42,7 +45,7 @@ namespace asset {
   class Unknown : public Media
     {
     protected:
-      Unknown (const Asset::Ident& idi, string name="", Time length=DUMMY_TIME);
+      Unknown (const Asset::Ident& idi, string name="", Duration length=DUMMY_TIME);
       friend class MediaFactory;
       
     public:
diff --git a/src/proc/engine/rendergraph.hpp b/src/proc/engine/rendergraph.hpp
index 718d3dfdb..a77eac68b 100644
--- a/src/proc/engine/rendergraph.hpp
+++ b/src/proc/engine/rendergraph.hpp
@@ -26,11 +26,16 @@
 
 #include "proc/common.hpp"
 #include "proc/state.hpp"
+#include "lib/time/timevalue.hpp"
 
 
 
 namespace engine {
   
+  using lib::time::TimeSpan;
+  using lib::time::FSecs;
+  using lib::time::Time;
+  
   class ExitNode;
   
   /**
@@ -41,11 +46,15 @@ namespace engine {
     protected:
       ExitNode * output;
       
-      /** begin of the timerange covered by this RenderGraph */
-      lumiera::Time start;
+      /** timerange covered by this RenderGraph */
+      TimeSpan segment_;
       
-      /**end (exclusive) of the timerange  */
-      lumiera::Time end;
+    public:
+      RenderGraph()
+        : segment_(Time::ZERO, FSecs(5))
+        {
+          UNIMPLEMENTED ("anything regarding the Fixture datastructure");
+        }
       
     };
   
diff --git a/src/proc/mobject/mobject-ref.hpp b/src/proc/mobject/mobject-ref.hpp
index e8c7cad5c..e4e5b3935 100644
--- a/src/proc/mobject/mobject-ref.hpp
+++ b/src/proc/mobject/mobject-ref.hpp
@@ -147,7 +147,7 @@ namespace mobject {
       /** resolves the referred placement to an 
        *  ExplicitPlacement and returns the found start time
        */
-      lumiera::Time const&
+      lib::time::Time const&
       getStartTime()
         {
           return pRef_.resolve().time;
diff --git a/src/proc/mobject/mobject.cpp b/src/proc/mobject/mobject.cpp
index f55c588aa..f844510fa 100644
--- a/src/proc/mobject/mobject.cpp
+++ b/src/proc/mobject/mobject.cpp
@@ -23,8 +23,10 @@
 
 #include "proc/mobject/mobject.hpp"
 #include "proc/mobject/session/mobjectfactory.hpp"
+#include "lib/time/timevalue.hpp"
 #include "lib/util.hpp"
 
+using lib::time::Time;
 using util::isnil;
 
 namespace mobject {
@@ -39,7 +41,7 @@ namespace mobject {
 
   
   MObject::MObject()
-    : length_()
+    : length_(Time::ZERO)
     , shortID_()
     { }
   
diff --git a/src/proc/mobject/mobject.hpp b/src/proc/mobject/mobject.hpp
index a8ea73313..c20bd64dd 100644
--- a/src/proc/mobject/mobject.hpp
+++ b/src/proc/mobject/mobject.hpp
@@ -31,6 +31,7 @@
 #include "proc/mobject/builder/buildertool.hpp"
 #include "proc/mobject/placement.hpp"
 #include "proc/asset.hpp"                    //TODO finally not needed?
+#include "lib/time/timevalue.hpp"
 
 #include <boost/noncopyable.hpp>
 #include <boost/operators.hpp>
@@ -68,10 +69,9 @@ namespace mobject {
       boost::equality_comparable< MObject >
     {
     protected:
-      typedef lumiera::Time Time;
+      typedef lib::time::Duration Duration;
       
-      // TODO: how to represent time intervals best?
-      Time length_;
+      Duration length_;
       
       mutable string shortID_;
       
@@ -93,7 +93,7 @@ namespace mobject {
       /** MObject self-test (usable for asserting) */
       virtual bool isValid()  const =0;
       
-      virtual Time& getLength() =0; ///< @todo how to deal with the time/length field?? ////TICKET #448
+      virtual Duration& getLength() =0;                                           ////////////////////TICKET #448
             
       virtual bool operator== (const MObject& oo)  const =0;  ///< needed for handling by lumiera::P
       
diff --git a/src/proc/mobject/placement.hpp b/src/proc/mobject/placement.hpp
index 5cd8206dc..94f6b2cca 100644
--- a/src/proc/mobject/placement.hpp
+++ b/src/proc/mobject/placement.hpp
@@ -69,6 +69,7 @@
 
 #include "pre.hpp"
 #include "lib/hash-indexed.hpp"
+#include "lib/time/timevalue.hpp"
 #include "proc/mobject/session/locatingpin.hpp"
 
 #include "proc/asset/pipe.hpp"   //////////////TICKET #109 : get rid of this
@@ -123,7 +124,7 @@ namespace mobject {
       typedef HashIndexed<Placement<MObject>, lib::hash::LuidH> HashInd;
       typedef shared_ptr<MObject> _SmartPtr;
       typedef void (*Deleter)(MObject*);
-      typedef lumiera::Time Time;
+      typedef lib::time::Time Time;
       typedef asset::shared_ptr<asset::Pipe> Pipe;   ////TICKET #109 : get rid of this
       
       
diff --git a/src/proc/mobject/session/abstractmo.hpp b/src/proc/mobject/session/abstractmo.hpp
index 53abf0466..1140f3c39 100644
--- a/src/proc/mobject/session/abstractmo.hpp
+++ b/src/proc/mobject/session/abstractmo.hpp
@@ -54,7 +54,7 @@ namespace session {
       
     public:
       
-      Time&
+      Duration&
       getLength()
         {
           return length_; 
diff --git a/src/proc/mobject/session/clip.cpp b/src/proc/mobject/session/clip.cpp
index af388fd9b..426cd8e57 100644
--- a/src/proc/mobject/session/clip.cpp
+++ b/src/proc/mobject/session/clip.cpp
@@ -25,6 +25,11 @@
 #include "proc/assetmanager.hpp"
 #include "proc/asset/media.hpp"
 #include "proc/asset/clip.hpp"
+#include "lib/time/mutation.hpp"
+#include "lib/util.hpp"
+
+using lib::time::Mutation;
+using util::isnil;
 
 namespace mobject {
 namespace session {
@@ -33,9 +38,8 @@ namespace session {
    *  Initially, this clip will cover the whole source media length.
    */
   Clip::Clip (const asset::Clip& clipDef, const Media& mediaDef)
-    : start_(0),
-      mediaDef_(mediaDef),
-      clipDef_(clipDef)
+    : mediaDef_(mediaDef)
+    , clipDef_(clipDef)
   {
     setupLength();
     throwIfInvalid();
@@ -50,7 +54,7 @@ namespace session {
   Clip::isValid ()  const
   {
     TODO ("check consistency of clip length def, implies accessing the underlying media def");
-    return length_ > Time(0);
+    return !isnil(length_);
   }
   
   
@@ -58,7 +62,7 @@ namespace session {
   Clip::setupLength()
   {
     TODO ("really calculate the length of a clip and set length field");
-    this->length_ = mediaDef_.getLength();
+    this->length_.accept (Mutation::changeDuration(mediaDef_.getLength()));
   }
   
   
diff --git a/src/proc/mobject/session/clip.hpp b/src/proc/mobject/session/clip.hpp
index 6a6251103..52e134926 100644
--- a/src/proc/mobject/session/clip.hpp
+++ b/src/proc/mobject/session/clip.hpp
@@ -25,6 +25,7 @@
 #define MOBJECT_SESSION_CLIP_H
 
 #include "proc/mobject/session/abstractmo.hpp"
+#include "lib/time/timevalue.hpp"
 
 
 namespace asset {
@@ -36,6 +37,8 @@ namespace mobject {
 namespace session {
   
   using asset::Media;
+  using lib::time::TimeVar;
+  
   typedef P<Media> PMedia;
   typedef P<asset::Clip> PClipAsset;
   
@@ -67,7 +70,7 @@ namespace session {
       
     protected:
       /** start position in source */
-      Time start_;
+      TimeVar start_;
       
       /** @todo using a mere ref here is against the scheme and only
           done as temporal solution, until we work out how to handle
diff --git a/src/proc/mobject/session/locatingpin.cpp b/src/proc/mobject/session/locatingpin.cpp
index 1c98c3df1..059e38290 100644
--- a/src/proc/mobject/session/locatingpin.cpp
+++ b/src/proc/mobject/session/locatingpin.cpp
@@ -189,7 +189,7 @@ namespace session {
   
   
   RelativeLocation& 
-  LocatingPin::operator() (PlaRef& refObj, Time offset)
+  LocatingPin::operator() (PlaRef& refObj, Offset const& offset)
   {
     return static_cast<RelativeLocation&> 
               (addChain (new RelativeLocation (refObj, offset)));
diff --git a/src/proc/mobject/session/locatingpin.hpp b/src/proc/mobject/session/locatingpin.hpp
index 04feae332..dc58ac944 100644
--- a/src/proc/mobject/session/locatingpin.hpp
+++ b/src/proc/mobject/session/locatingpin.hpp
@@ -48,6 +48,7 @@
 
 
 #include "proc/common.hpp"
+#include "lib/time/timevalue.hpp"
 
 #include <utility>
 #include <tr1/memory>
@@ -96,7 +97,9 @@ namespace mobject {
     class LocatingPin
       {
       protected:
-        typedef lumiera::Time Time;
+        typedef lib::time::Time Time;
+        typedef lib::time::TimeVar TimeVar;
+        typedef lib::time::Offset Offset;
         typedef Time* Track; //TODO dummy declaration; we don't use Tracks as first-class entity any longer
         typedef std::tr1::shared_ptr<asset::Pipe> Pipe;
         typedef std::pair<Time,Pipe> SolutionData;  //TICKET #100 (ichthyo considers better passing of solution by subclass)
@@ -119,7 +122,7 @@ namespace mobject {
         /* Factory functions for adding LocatingPins */
         
         FixedLocation&    operator() (Time start, Track track=0);
-        RelativeLocation& operator() (PlacementRef<MObject>& refObj, Time offset=Time(0));   //////////TODO: warning, just a dummy placeholder for now!!
+        RelativeLocation& operator() (PlacementRef<MObject>& refObj, Offset const& offset=Offset(Time::ZERO));   //////////TODO: warning, just a dummy placeholder for now!!
         
         LocatingPin (const LocatingPin&);
         LocatingPin& operator= (const LocatingPin&);
@@ -145,8 +148,8 @@ protected:
          */  
         struct LocatingSolution
           {
-            Time minTime;
-            Time maxTime;
+            TimeVar minTime;
+            TimeVar maxTime;
             Track minTrack; // TODO don't use Tracks
             Track maxTrack;
             bool impo;
diff --git a/src/proc/mobject/session/relativelocation.hpp b/src/proc/mobject/session/relativelocation.hpp
index 46b2a6d4b..bea3e134b 100644
--- a/src/proc/mobject/session/relativelocation.hpp
+++ b/src/proc/mobject/session/relativelocation.hpp
@@ -33,6 +33,8 @@
 namespace mobject {
 namespace session {
   
+  using lib::time::Offset;
+  
   
   /**
    * @todo just a design sketch, nothing finished yet.
@@ -56,14 +58,14 @@ namespace session {
       };
       
     protected:
-      RelativeLocation (PlaRef const& a, Time ofs) : anchor_(a), offset_(ofs) { }
+      RelativeLocation (PlaRef const& a, Offset const& ofs) : anchor_(a), offset_(ofs) { }
       friend class LocatingPin;
       
       /** the kind of relation denoted by this Placement */
       RelType relType;
       
       /** Offset the actual position by this (time) value relative to the anchor point. */
-      Time offset_;
+      Offset offset_;
       //TODO: suitable representation?
       
       
diff --git a/src/proc/mobject/session/segment.hpp b/src/proc/mobject/session/segment.hpp
index 3a0835c87..9c39533e2 100644
--- a/src/proc/mobject/session/segment.hpp
+++ b/src/proc/mobject/session/segment.hpp
@@ -28,6 +28,7 @@
 
 #include "proc/common.hpp"
 #include "proc/mobject/explicitplacement.hpp"
+#include "lib/time/timevalue.hpp"
 
 
 using std::list;
@@ -46,12 +47,10 @@ namespace mobject {
     class Segment
       {
       protected:
-        typedef lumiera::Time Time;
+        typedef lib::time::TimeSpan Span;
 
         /** begin of this timeline segment. */
-        Time start;
-        /** duration (span) of this timeline segment. */
-        Time length;
+        Span span_;
 
         /** relevant MObjects comprising this segment. */
         list<ExplicitPlacement> elements;
diff --git a/src/proc/mobject/session/track.cpp b/src/proc/mobject/session/track.cpp
index 73e811b90..78ca7a52a 100644
--- a/src/proc/mobject/session/track.cpp
+++ b/src/proc/mobject/session/track.cpp
@@ -32,7 +32,7 @@ namespace session {
    *  will be set to 0 
    */
   Track::Track (TrackID const& trackID)
-    : start_(0)
+    : start_(Time::ZERO)                     //////////////////////////////////TODO something more inspired please
     , id_(trackID)
   {
     throwIfInvalid();
diff --git a/src/proc/mobject/session/track.hpp b/src/proc/mobject/session/track.hpp
index 60fb8afa5..998c51899 100644
--- a/src/proc/mobject/session/track.hpp
+++ b/src/proc/mobject/session/track.hpp
@@ -26,6 +26,7 @@
 
 #include "proc/mobject/session/meta.hpp"
 #include "proc/asset/entry-id.hpp"
+#include "lib/time/timevalue.hpp"
 
 
 
@@ -33,6 +34,7 @@ namespace mobject {
 namespace session {     //////////////////////////////////////////////////////TICKET #637
     
     using lumiera::P;
+    using lib::time::Time;
     
     class Track;
     
@@ -52,6 +54,9 @@ namespace session {
     using asset::TrackID;
     
   
+                        //////////////////////////////////////////////////////TICKET #646
+                        //////////////////////////////////////////////////////TICKET #715
+    
     /**
      * A Track is grouping device within the Session.
      * The corresponding Placement by which this Track object is referred
@@ -73,7 +78,7 @@ namespace session {
      */
     class Track : public Meta
       {
-        Time start_;
+        Time start_;    /////////////////////////////////TODO: this doesn't belong here. The start position is governed by the Placement!!!
         TrackID id_;