diff --git a/src/gui/panels/timeline-panel.cpp b/src/gui/panels/timeline-panel.cpp
index 5c79bbe44..9441e8969 100644
--- a/src/gui/panels/timeline-panel.cpp
+++ b/src/gui/panels/timeline-panel.cpp
@@ -29,9 +29,8 @@
 #include "gui/model/project.hpp"
 #include "gui/controller/controller.hpp"
 
-extern "C" {
 #include "lib/time.h"
-}
+
 
 using namespace Gtk;
 using namespace sigc;
diff --git a/src/gui/widgets/timeline/timeline-ruler.cpp b/src/gui/widgets/timeline/timeline-ruler.cpp
index 63d6ecc7a..c01835c71 100644
--- a/src/gui/widgets/timeline/timeline-ruler.cpp
+++ b/src/gui/widgets/timeline/timeline-ruler.cpp
@@ -27,9 +27,8 @@
 #include "gui/window-manager.hpp"
 #include "gui/util/cairo-util.hpp"
 
-extern "C" {
 #include "lib/time.h"
-}
+
 
 using namespace Gtk;
 using namespace Cairo;
diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am
index 8374eab38..fe64f516a 100644
--- a/src/lib/Makefile.am
+++ b/src/lib/Makefile.am
@@ -59,7 +59,7 @@ liblumiera_la_SOURCES =					\
 	$(liblumiera_la_srcdir)/test/suite.cpp		\
 	$(liblumiera_la_srcdir)/test/test-helper.cpp	\
 	$(liblumiera_la_srcdir)/test/testoption.cpp	\
-	$(liblumiera_la_srcdir)/time.c			\
+	$(liblumiera_la_srcdir)/time.cpp		\
 	$(liblumiera_la_srcdir)/time/lumitime.cpp	\
 	$(liblumiera_la_srcdir)/time/quantiser.cpp	\
 	$(liblumiera_la_srcdir)/time/timecode.cpp	\
diff --git a/src/lib/lumitime-fmt.hpp b/src/lib/lumitime-fmt.hpp
index 20b24f951..b916c13a6 100644
--- a/src/lib/lumitime-fmt.hpp
+++ b/src/lib/lumitime-fmt.hpp
@@ -45,13 +45,11 @@
 #define LUMIERA_LUMITIME_FMT_H
 
 #include "lib/lumitime.hpp"
-
-extern "C" {
 #include "lib/time.h"
-}
 
 #include <iostream>
 
+
 namespace lumiera {
 
 
diff --git a/src/lib/time.c b/src/lib/time.cpp
similarity index 98%
rename from src/lib/time.c
rename to src/lib/time.cpp
index 6f62a8ada..a85e2d1ea 100644
--- a/src/lib/time.c
+++ b/src/lib/time.cpp
@@ -19,12 +19,14 @@
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-#include <nobug.h>
 #include "lib/time.h"
+#include "lib/error.hpp"
+extern "C" {
 #include "lib/tmpbuf.h"
+}
 
-#include <math.h>
 #include <limits.h>
+#include <math.h>
 
 
 /* GAVL_TIME_SCALE is the correct factor or dividend when using gavl_time_t for
diff --git a/src/lib/time.h b/src/lib/time.h
index eabc4d5f8..666fa4206 100644
--- a/src/lib/time.h
+++ b/src/lib/time.h
@@ -19,17 +19,66 @@
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
+/** @file time.h
+ ** Common functions for handling of time values.
+ ** Working with time values in sexagesimal format, quantising time and converting
+ ** to/from common timecode formats can be tricky to get right. Thus the goal is
+ ** to concentrate the actual bits of math for these operations into a small number
+ ** of library functions, which are easy to test thoroughly in isolation.
+ ** 
+ ** Built on top of that, the actual time handling in the GUI and within the Lumiera
+ ** session is mostly confined to use the opaque lib::time::Time wrapper objects.
+ ** When time values actually need to be \em quantised (aligned to a frame grid),
+ ** this is expressed at the API through using the lib::time::QuTime type, which
+ ** then in turn can be materialised into a number of \em timecode formats.
+ ** These definitions ensure that whenever an actual quantisation (rounding)
+ ** operation is performed, the link to the appropriate time grid is available,
+ ** so that multiple output or rendering operations can use differing time origins
+ ** and frame rates simultaneously on the same model.
+ ** 
+ ** The Lumiera backend functions mostly operate on raw frame counts, which in this
+ ** model are defined to be a special kind of timecode, and thus dependent on a
+ ** preceding time quantisation.
+ ** 
+ ** 
+ ** @see lib::time::Time
+ ** @see timequant.hpp
+ ** @see TimeValue_test
+ ** 
+ */
+
+
 #ifndef LUMIERA_TIME_H
 #define LUMIERA_TIME_H
 
 #include <inttypes.h>
 #include <gavl/gavl.h>
 
+#ifdef __cplusplus /*=================== C++ facilities ===================== */
+#include "lib/time/timevalue.hpp"
+
+
 /**
- * Formats a time in a safeclib tmpbuf in HH:MM:SS:mmm format.
- * @param size maximal length for the string
- * @param the time value to print
- * @return safeclib temporary buffer containing the constructed of the string
+ * Converts a fraction of seconds to Lumiera's internal opaque time scale.
+ * @param fractionalSeconds given as rational number
+ */
+inline gavl_time_t
+lumiera_rational_to_time (lib::time::FSecs const& fractionalSeconds)
+{
+  return boost::rational_cast<gavl_time_t> (GAVL_TIME_SCALE * fractionalSeconds);
+}
+
+
+
+
+
+extern "C" {    /* ===================== C interface ======================== */
+#endif
+
+
+/**
+ * Formats a time value in H:MM:SS.mmm format into a temporary buffer.
+ * @return safeclib temporary buffer containing formatted time string
  */
 char*
 lumiera_tmpbuf_print_time (gavl_time_t time);
@@ -41,19 +90,19 @@ lumiera_tmpbuf_print_time (gavl_time_t time);
  * as zero. Each interval includes its lower bound, but excludes its upper bound.
  * @param grid spacing of the grid intervals, measured in GAVL_TIME_SCALE
  * @return number of the grid interval containing the given time.
- * @warning the resulting value is limited such as to fit into a 64bit long 
+ * @warning the resulting value is limited to (Time::Min, Time::MAX) 
  */
 int64_t
 lumiera_quantise_frames (gavl_time_t time, double grid, gavl_time_t origin);
 
 /**
- * Similar to #lumiera_quantise_frames, but returns a grid aligned \em time value 
+ * Similar to #lumiera_quantise_frames, but returns a grid aligned \em time value
  * @return time of start of the grid interval containing the given time, 
  *         but measured relative to the origin
  * @warning because the resulting value needs to be limited to fit into a 64bit long,
  *         the addressable time range can be considerably reduced. For example, if
- *         origin = LLONG_MIN, then all original time values above zero will be
- *         clipped, because the result, relative to origin, needs to be <= LLONG_MAX 
+ *         origin = Time::MIN, then all original time values above zero will be
+ *         clipped, because the result, relative to origin, needs to be <= Time::MAX 
  */
 gavl_time_t
 lumiera_quantise_time (gavl_time_t time, double grid, gavl_time_t origin);
@@ -65,24 +114,28 @@ gavl_time_t
 lumiera_build_time (long millis, uint secs, uint mins, uint hours);
 
 /**
- * Get the hour part of given time.
+ * Extract the hour part of given time.
  */
 int lumiera_time_hours(gavl_time_t time);
 
 /**
- * Get the minute part of given time.
+ * Extract the minute part of given time.
  */
 int lumiera_time_minutes(gavl_time_t time);
 
 /**
- * Get the seconds part of given time.
+ * Extract the seconds part of given time.
  */
 int lumiera_time_seconds(gavl_time_t time);
 
 /**
- * Get the milliseconds part of given time.
+ * Extract the milliseconds part of given time.
  */
 int lumiera_time_millis(gavl_time_t time);
 
-#endif
 
+
+#ifdef __cplusplus
+}//extern "C"
+#endif
+#endif
diff --git a/src/lib/time/lumitime.cpp b/src/lib/time/lumitime.cpp
index 15444a60c..53338e3a6 100644
--- a/src/lib/time/lumitime.cpp
+++ b/src/lib/time/lumitime.cpp
@@ -23,10 +23,7 @@
 
 #include "lib/lumitime.hpp"
 #include "lib/time/timevalue.hpp"
-
-extern "C" {
 #include "lib/time.h"
-}
 
 #include <limits>
 #include <string>
diff --git a/src/lib/time/quantiser.cpp b/src/lib/time/quantiser.cpp
index c1608184f..02ef85be8 100644
--- a/src/lib/time/quantiser.cpp
+++ b/src/lib/time/quantiser.cpp
@@ -24,10 +24,7 @@
 #include "lib/time/quantiser.hpp"
 #include "lib/time/timevalue.hpp"
 #include "lib/time/timequant.hpp"
-
-extern "C" {
 #include "lib/time.h"
-}
 
 #include <boost/rational.hpp>
 
diff --git a/src/lib/time/timecode.cpp b/src/lib/time/timecode.cpp
index 3bb80e697..37e00a9ea 100644
--- a/src/lib/time/timecode.cpp
+++ b/src/lib/time/timecode.cpp
@@ -26,10 +26,7 @@
 #include "lib/time/timevalue.hpp"
 #include "lib/time/timequant.hpp"
 #include "lib/time/formats.hpp"
-
-extern "C" {
 #include "lib/time.h"
-}
 
 
 using std::string;
diff --git a/tests/library/test-time.c b/tests/library/test-time.c
index 4ce8b63bb..52ce79279 100644
--- a/tests/library/test-time.c
+++ b/tests/library/test-time.c
@@ -21,8 +21,8 @@
 
 typedef unsigned int uint;
 
-#include "lib/time.h"
 #include "tests/test.h"
+#include "lib/time.h"
 
 #include <nobug.h>