diff --git a/gtk2_ardour/ardour_ui2.cc b/gtk2_ardour/ardour_ui2.cc
index df344a5124..37f1a9865a 100644
--- a/gtk2_ardour/ardour_ui2.cc
+++ b/gtk2_ardour/ardour_ui2.cc
@@ -366,8 +366,8 @@ ARDOUR_UI::setup_transport ()
 	set_size_request_to_display_given_text (io_latency_value, "1000 spl", 0, 0);
 
 	/* connect signals */
-	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (primary_clock, &MainClock::set), false, timecnt_t::zero (Temporal::AudioTime)));
-	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (secondary_clock, &MainClock::set), false, timecnt_t::zero (Temporal::AudioTime)));
+	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (primary_clock, &MainClock::set), false));
+	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (secondary_clock, &MainClock::set), false));
 
 	primary_clock->ValueChanged.connect (sigc::mem_fun(*this, &ARDOUR_UI::primary_clock_value_changed));
 	secondary_clock->ValueChanged.connect (sigc::mem_fun(*this, &ARDOUR_UI::secondary_clock_value_changed));
diff --git a/gtk2_ardour/ardour_ui3.cc b/gtk2_ardour/ardour_ui3.cc
index 4cd2ef1585..67c4f69263 100644
--- a/gtk2_ardour/ardour_ui3.cc
+++ b/gtk2_ardour/ardour_ui3.cc
@@ -185,12 +185,12 @@ ARDOUR_UI::update_transport_clocks (samplepos_t p)
 			primary_clock->set (pos);
 			break;
 		case DeltaEditPoint:
-			primary_clock->set (pos, false, timecnt_t (editor->get_preferred_edit_position (EDIT_IGNORE_PHEAD)));
+			primary_clock->set_duration (pos.distance (editor->get_preferred_edit_position (EDIT_IGNORE_PHEAD)), false);
 			break;
 		case DeltaOriginMarker:
 			{
 				Location* loc = _session->locations()->clock_origin_location ();
-				primary_clock->set (pos, false, timecnt_t (loc ? loc->start_sample() : 0));
+				primary_clock->set_duration (pos.distance (loc->start()));
 			}
 			break;
 	}
@@ -200,12 +200,12 @@ ARDOUR_UI::update_transport_clocks (samplepos_t p)
 			secondary_clock->set (pos);
 			break;
 		case DeltaEditPoint:
-			secondary_clock->set (pos, false, timecnt_t (editor->get_preferred_edit_position (EDIT_IGNORE_PHEAD)));
+			secondary_clock->set_duration (pos.distance (editor->get_preferred_edit_position (EDIT_IGNORE_PHEAD)), false);
 			break;
 		case DeltaOriginMarker:
 			{
 				Location* loc = _session->locations()->clock_origin_location ();
-				secondary_clock->set (pos, false, timecnt_t (loc ? loc->start_sample() : 0));
+				secondary_clock->set_duration (pos.distance (loc->start()));
 			}
 			break;
 	}
diff --git a/gtk2_ardour/ardour_ui_options.cc b/gtk2_ardour/ardour_ui_options.cc
index 8b262dbd58..68de11e1df 100644
--- a/gtk2_ardour/ardour_ui_options.cc
+++ b/gtk2_ardour/ardour_ui_options.cc
@@ -380,21 +380,17 @@ ARDOUR_UI::parameter_changed (std::string p)
 		if (editor) editor->toggle_meter_updating();
 	} else if (p == "primary-clock-delta-mode") {
 		if (UIConfiguration::instance().get_primary_clock_delta_mode() != NoDelta) {
-			primary_clock->set_is_duration (true, timepos_t());
 			primary_clock->set_editable (false);
 			primary_clock->set_widget_name ("transport delta");
 		} else {
-			primary_clock->set_is_duration (false, timepos_t());
 			primary_clock->set_editable (true);
 			primary_clock->set_widget_name ("transport");
 		}
 	} else if (p == "secondary-clock-delta-mode") {
 		if (UIConfiguration::instance().get_secondary_clock_delta_mode() != NoDelta) {
-			secondary_clock->set_is_duration (true, timepos_t());
 			secondary_clock->set_editable (false);
 			secondary_clock->set_widget_name ("secondary delta");
 		} else {
-			secondary_clock->set_is_duration (false, timepos_t());
 			secondary_clock->set_editable (true);
 			secondary_clock->set_widget_name ("secondary");
 		}
diff --git a/gtk2_ardour/audio_clock.cc b/gtk2_ardour/audio_clock.cc
index b25e1f6c22..fdd1e795e7 100644
--- a/gtk2_ardour/audio_clock.cc
+++ b/gtk2_ardour/audio_clock.cc
@@ -101,7 +101,6 @@ AudioClock::AudioClock (const string& clock_name, bool transient, const string&
 	, corner_radius (4)
 	, font_size (10240)
 	, editing (false)
-	, bbt_reference_time (timepos_t::from_superclock (-1)) /* needs to be some negative value but SR may not be available at init */
 	, last_pdelta (0)
 	, last_sdelta (0)
 	, dragging (false)
@@ -120,7 +119,7 @@ AudioClock::AudioClock (const string& clock_name, bool transient, const string&
 
 	_mode = BBT; /* lie to force mode switch */
 	set_mode (Timecode);
-	AudioClock::set (last_when, true);
+	AudioClock::set (last_when(), true);
 
 	if (!is_transient) {
 		clocks.push_back (this);
@@ -523,7 +522,7 @@ AudioClock::end_edit (bool modify)
 
 			case BBT:
 				if (is_duration) {
-					pos = sample_duration_from_bbt_string (bbt_reference_time, edit_string);
+					pos = sample_duration_from_bbt_string (last_when(), edit_string);
 				} else {
 					pos = samples_from_bbt_string (timepos_t(), edit_string);
 				}
@@ -807,7 +806,7 @@ AudioClock::end_edit_relative (bool add)
 void
 AudioClock::tempo_map_changed ()
 {
-	AudioClock::set (last_when, true);
+	AudioClock::set (last_when(), true);
 }
 
 void
@@ -819,69 +818,71 @@ AudioClock::session_configuration_changed (std::string p)
 	}
 
 	if (p == "sync-source" || p == "external-sync") {
-		AudioClock::set (current_time(), true);
-		return;
-	}
-
-	if (p != "timecode-offset" && p != "timecode-offset-negative") {
-		return;
-	}
-
-	timepos_t current;
-
-	switch (_mode) {
-	case Timecode:
 		if (is_duration) {
-			current = timepos_t (current_duration ());
+			AudioClock::set_duration (current_duration(), true);
 		} else {
-			current = current_time ();
+			AudioClock::set (current_time(), true);
+		}
+		return;
+	}
+
+	if (p == "timecode-offset" && p == "timecode-offset-negative") {
+		switch (_mode) {
+		case Timecode:
+			if (is_duration) {
+				AudioClock::set_duration (current_duration(), true);
+			} else {
+				AudioClock::set (current_time(), true);
+			}
+			break;
+		default:
+			break;
 		}
-		AudioClock::set (current, true);
-		break;
-	default:
-		break;
 	}
 }
 
 void
-AudioClock::set (timepos_t const & w, bool force, timecnt_t const & offset)
+AudioClock::set_duration (Temporal::timecnt_t const & dur, bool force)
 {
-	timepos_t when (w);
+	is_duration = true;
 
 	if ((!force && !get_visible()) || !_session) {
 		return;
 	}
 
-	_offset = offset;
-	if (is_duration) {
-		when = when.earlier (offset);
+	timepos_t when;
+
+	/* extent semantics, not length */
+
+	timecnt_t d;
+
+	/* durations for timecode display should use extent, not length
+	 *
+	 * reminder: length = end - start ; extent = end - start - 1
+	 *
+	 * start + length = end
+	 * start + extent = last_point_inside duration
+	 */
+
+	switch (_mode) {
+	case Timecode:
+		d = dur.is_zero() ? dur : dur.decrement_by_domain ();
+		break;
+	default:
+		d = dur;
+		break;
 	}
 
-	if (when > _limit_pos) {
-		when = _limit_pos;
-	} else if (when < -_limit_pos) {
-		when = -_limit_pos;
+	/* Converting a negative duration to a position throws */
+
+	if (d.is_negative()) {
+		when = timepos_t (d);
+	} else {
+		when = -timepos_t (-d);
 	}
 
-	if (when == last_when && !force) {
-#if 0 // XXX return if no change and no change forced. verify Aug/2014
-		if (_mode != Timecode && _mode != MinSec) {
-			/* may need to force display of TC source
-			 * time, so don't return early.
-			 */
-			/* ^^ Why was that?,  delta times?
-			 * Timecode FPS, pull-up/down, etc changes
-			 * trigger a 'session_property_changed' which
-			 * eventually calls set(last_when, true)
-			 *
-			 * re-rendering the clock every 40ms or so just
-			 * because we can is not ideal.
-			 */
-			return;
-		}
-#else
+	if (when == last_when() && !force) {
 		return;
-#endif
 	}
 
 	bool btn_en = false;
@@ -894,7 +895,7 @@ AudioClock::set (timepos_t const & w, bool force, timecnt_t const & offset)
 			break;
 
 		case BBT:
-			set_bbt (when, offset, force);
+			set_bbt (dur, force);
 			btn_en = true;
 			break;
 
@@ -913,12 +914,61 @@ AudioClock::set (timepos_t const & w, bool force, timecnt_t const & offset)
 	}
 
 	finish_set (when, btn_en);
+	last_time = dur;
 }
 
 void
-AudioClock::set_duration (Temporal::timecnt_t const & d, bool force, Temporal::timecnt_t const & offset)
+AudioClock::set (timepos_t const & w, bool force)
 {
-	set (timepos_t (d), force, offset);
+	is_duration = false;
+
+	timepos_t when (w);
+
+	if ((!force && !get_visible()) || !_session) {
+		return;
+	}
+
+	if (when > _limit_pos) {
+		when = _limit_pos;
+	} else if (when < -_limit_pos) {
+		when = -_limit_pos;
+	}
+
+	if (when == last_when() && !force) {
+		return;
+	}
+
+	bool btn_en = false;
+
+	if (!editing) {
+
+		switch (_mode) {
+		case Timecode:
+			set_timecode (when, force);
+			break;
+
+		case BBT:
+			set_bbt (timecnt_t (when), force);
+			btn_en = true;
+			break;
+
+		case MinSec:
+			set_minsec (when, force);
+			break;
+
+		case Seconds:
+			set_seconds (when, force);
+			break;
+
+		case Samples:
+			set_samples (when, force);
+			break;
+		}
+	}
+
+	finish_set (when, btn_en);
+
+	last_time = timecnt_t (last_time.distance(), when);
 }
 
 void
@@ -947,7 +997,6 @@ AudioClock::finish_set (Temporal::timepos_t const & when, bool btn_en)
 	}
 
 	queue_draw ();
-	last_when = when;
 }
 
 void
@@ -1209,49 +1258,44 @@ AudioClock::set_timecode (timepos_t const & w, bool /*force*/)
 }
 
 void
-AudioClock::set_bbt (timepos_t const & w, timecnt_t const & o, bool /*force*/)
+AudioClock::set_bbt (timecnt_t const & w, bool /*force*/)
 {
-	timepos_t when (w);
-	timecnt_t offset (o);
+	timepos_t pos (w);
 	char buf[64];
 	Temporal::BBT_Time BBT;
 	bool negative = false;
 
-	if (_off || when >= _limit_pos || when < -_limit_pos) {
+	if (_off || pos >= _limit_pos || pos < -_limit_pos) {
 		_layout->set_text (" ---|--|----");
 		_left_btn.set_text ("", false);
 		_right_btn.set_text ("", false);
 		return;
 	}
 
-	if (when.is_negative ()) {
-		when = -when;
+	if (pos.is_negative ()) {
+		pos = -pos;
 		negative = true;
 	}
 
 	/* handle a common case */
 
 	if (is_duration) {
-		if (when.is_zero ()) {
+		if (pos.is_zero ()) {
 			BBT.bars = 0;
 			BBT.beats = 0;
 			BBT.ticks = 0;
 		} else {
 			TempoMap::SharedPtr tmap (TempoMap::use());
 
-			if (offset.is_zero ()) {
-				offset = timecnt_t (bbt_reference_time);
-			}
-
-			const int divisions = tmap->meter_at (timepos_t (offset)).divisions_per_bar();
+			const int divisions = tmap->meter_at (w.position()).divisions_per_bar();
 			Temporal::BBT_Time sub_bbt;
 
 			if (negative) {
-				BBT = tmap->bbt_at (timepos_t (tmap->quarters_at (timepos_t (offset))));
-				sub_bbt = tmap->bbt_at (timepos_t (offset - when));
+				BBT = tmap->bbt_at (timepos_t (tmap->quarters_at (w.position())));
+				sub_bbt = tmap->bbt_at (last_when().earlier (w.position()));
 			} else {
-				BBT = tmap->bbt_at (timepos_t (tmap->quarters_at (when + offset)));
-				sub_bbt = tmap->bbt_at (timepos_t (offset));
+				BBT = tmap->bbt_at (timepos_t (tmap->quarters_at (w.end())));
+				sub_bbt = tmap->bbt_at (w.position());
 			}
 
 			BBT.bars -= sub_bbt.bars;
@@ -1276,7 +1320,7 @@ AudioClock::set_bbt (timepos_t const & w, timecnt_t const & o, bool /*force*/)
 			}
 		}
 	} else {
-		BBT = TempoMap::use()->bbt_at (when);
+		BBT = TempoMap::use()->bbt_at (pos);
 	}
 
 	if (negative) {
@@ -1290,13 +1334,6 @@ AudioClock::set_bbt (timepos_t const & w, timecnt_t const & o, bool /*force*/)
 	_layout->set_text (buf);
 
 	if (_with_info) {
-		timepos_t pos;
-
-		if (bbt_reference_time.is_negative ()) {
-			pos = when;
-		} else {
-			pos = bbt_reference_time;
-		}
 
 		TempoMetric m (TempoMap::use()->metric_at (pos));
 
@@ -1356,7 +1393,7 @@ AudioClock::set_session (Session *s)
 			}
 		}
 
-		AudioClock::set (last_when, true);
+		AudioClock::set (last_when(), true);
 	}
 }
 
@@ -1927,7 +1964,7 @@ AudioClock::get_incremental_step (Field field, timepos_t const & pos)
 timepos_t
 AudioClock::current_time () const
 {
-	return last_when;
+	return last_when();
 }
 
 timecnt_t
@@ -1944,7 +1981,7 @@ AudioClock::current_duration (timepos_t pos) const
 	case MinSec:
 	case Seconds:
 	case Samples:
-		ret = timecnt_t (last_when, pos);
+		ret = timecnt_t (last_when(), pos);
 		break;
 	}
 
@@ -1954,28 +1991,28 @@ AudioClock::current_duration (timepos_t pos) const
 bool
 AudioClock::bbt_validate_edit (string & str)
 {
-	AnyTime any;
+	BBT_Time bbt;
 
-	if (sscanf (str.c_str(), BBT_SCANF_FORMAT, &any.bbt.bars, &any.bbt.beats, &any.bbt.ticks) != 3) {
+	if (sscanf (str.c_str(), BBT_SCANF_FORMAT, &bbt.bars, &bbt.beats, &bbt.ticks) != 3) {
 		return false;
 	}
 
-	if (any.bbt.ticks > Temporal::ticks_per_beat) {
+	if (bbt.ticks > Temporal::ticks_per_beat) {
 		return false;
 	}
 
-	if (!is_duration && any.bbt.bars == 0) {
+	if (!is_duration && bbt.bars == 0) {
 		return false;
 	}
 
-	if (!is_duration && any.bbt.beats == 0) {
+	if (!is_duration && bbt.beats == 0) {
 		/* user could not have mean zero beats because for a
 		 * non-duration clock that's impossible. Assume that they
 		 * mis-entered things and meant Bar|1|ticks
 		 */
 
 		char buf[128];
-		snprintf (buf, sizeof (buf), "%" PRIu32 "|%" PRIu32 "|%" PRIu32, any.bbt.bars, 1, any.bbt.ticks);
+		snprintf (buf, sizeof (buf), "%" PRIu32 "|%" PRIu32 "|%" PRIu32, bbt.bars, 1, bbt.ticks);
 		str = buf;
 	}
 
@@ -2278,7 +2315,7 @@ AudioClock::set_mode (Mode m, bool noemit)
 		break;
 	}
 
-	AudioClock::set (last_when, true);
+	AudioClock::set (last_when(), true);
 
 	if (!is_transient && !noemit) {
 		ModeChanged (); /* EMIT SIGNAL (the static one)*/
@@ -2287,12 +2324,6 @@ AudioClock::set_mode (Mode m, bool noemit)
 	mode_changed (); /* EMIT SIGNAL (the member one) */
 }
 
-void
-AudioClock::set_bbt_reference (timepos_t const & pos)
-{
-	bbt_reference_time = pos;
-}
-
 void
 AudioClock::on_style_changed (const Glib::RefPtr<Gtk::Style>& old_style)
 {
@@ -2319,28 +2350,6 @@ AudioClock::set_editable (bool yn)
 	editable = yn;
 }
 
-void
-AudioClock::set_is_duration (bool yn, timepos_t const & p)
-{
-	if (yn == is_duration) {
-		if (yn) {
-			/* just reset position */
-			duration_position = p;
-		}
-
-		return;
-	}
-
-	is_duration = yn;
-	if (yn) {
-		duration_position = p;
-	} else {
-		duration_position = timepos_t ();
-	}
-
-	set (last_when, true);
-}
-
 void
 AudioClock::set_off (bool yn)
 {
@@ -2350,11 +2359,15 @@ AudioClock::set_off (bool yn)
 
 	_off = yn;
 
-	/* force a redraw. last_when will be preserved, but the clock text will
+	/* force a redraw. last_time will be preserved, but the clock text will
 	 * change
 	 */
 
-	AudioClock::set (last_when, true);
+	if (is_duration) {
+		AudioClock::set_duration (last_time, true);
+	} else {
+		AudioClock::set (last_when(), true);
+	}
 }
 
 void
diff --git a/gtk2_ardour/audio_clock.h b/gtk2_ardour/audio_clock.h
index f671d8c6b9..48f30dae89 100644
--- a/gtk2_ardour/audio_clock.h
+++ b/gtk2_ardour/audio_clock.h
@@ -73,14 +73,14 @@ class AudioClock : public CairoWidget, public ARDOUR::SessionHandlePtr
 
 	void focus ();
 
-	virtual void set (Temporal::timepos_t const &, bool force = false, Temporal::timecnt_t const & offset = Temporal::timecnt_t());
-	void set_duration (Temporal::timecnt_t const &, bool force = false, Temporal::timecnt_t const & offset = Temporal::timecnt_t());
+	/* overriden by MainClock */
+	virtual void set (Temporal::timepos_t const &, bool force = false);
+	void set_duration (Temporal::timecnt_t const &, bool force = false);
 
 	void set_from_playhead ();
 	void locate ();
 	void set_mode (Mode, bool noemit = false);
 	void set_bbt_reference (Temporal::timepos_t const &);
-	void set_is_duration (bool, Temporal::timepos_t const &);
 
 	void copy_text_to_clipboard () const;
 
@@ -199,8 +199,9 @@ class AudioClock : public CairoWidget, public ARDOUR::SessionHandlePtr
 	std::string pre_edit_string;
 	std::string input_string;
 
-	Temporal::timepos_t bbt_reference_time;
-	Temporal::timepos_t last_when;
+	Temporal::timecnt_t last_time;
+	Temporal::timepos_t last_when() const { return last_time.position(); }
+
 	bool last_pdelta;
 	bool last_sdelta;
 
@@ -221,7 +222,7 @@ class AudioClock : public CairoWidget, public ARDOUR::SessionHandlePtr
 
 	void set_slave_info ();
 	void set_timecode (Temporal::timepos_t const &, bool);
-	void set_bbt (Temporal::timepos_t const &, Temporal::timecnt_t const &, bool);
+	void set_bbt (Temporal::timecnt_t const &, bool);
 	void set_minsec (Temporal::timepos_t const &, bool);
 	void set_seconds (Temporal::timepos_t const &, bool);
 	void set_samples (Temporal::timepos_t const &, bool);
diff --git a/gtk2_ardour/big_clock_window.cc b/gtk2_ardour/big_clock_window.cc
index ecb3c12492..dfabc440f7 100644
--- a/gtk2_ardour/big_clock_window.cc
+++ b/gtk2_ardour/big_clock_window.cc
@@ -39,7 +39,7 @@ BigClockWindow::BigClockWindow (AudioClock& c)
 	: ArdourWindow (_("Big Clock"))
 	, clock (c)
 {
-	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (clock, &AudioClock::set), false, Temporal::timecnt_t()));
+	ARDOUR_UI::Clock.connect (sigc::bind (sigc::mem_fun (clock, &AudioClock::set), false));
 
 	clock.set_corner_radius (0.0);
 
diff --git a/gtk2_ardour/edit_note_dialog.cc b/gtk2_ardour/edit_note_dialog.cc
index 13ab3930d6..8e11ccebea 100644
--- a/gtk2_ardour/edit_note_dialog.cc
+++ b/gtk2_ardour/edit_note_dialog.cc
@@ -97,9 +97,7 @@ EditNoteDialog::EditNoteDialog (MidiRegionView* rv, set<NoteBase*> n)
 	_time_clock.set_session (_region_view->get_time_axis_view().session ());
 	_time_clock.set_mode (AudioClock::BBT);
 
-	timecnt_t dur = _region_view->source_relative_distance (timecnt_t ((*_events.begin())->note()->time(), timepos_t()), BeatTime);
-	timepos_t pos = _region_view->region()->source_position() + dur;
-
+	const timepos_t pos (_region_view->region_relative_distance (timecnt_t ((*_events.begin())->note()->time (), timepos_t()), BeatTime));
 	_time_clock.set (pos, true);
 
 	l = manage (left_aligned_label (_("Length")));
@@ -110,15 +108,7 @@ EditNoteDialog::EditNoteDialog (MidiRegionView* rv, set<NoteBase*> n)
 
 	_length_clock.set_session (_region_view->get_time_axis_view().session ());
 	_length_clock.set_mode (AudioClock::BBT);
-
-	dur = _region_view->region_relative_distance (timecnt_t ((*_events.begin())->note()->end_time (), timepos_t()), BeatTime);
-	pos = _region_view->region()->position() + dur;
-	timecnt_t offset;
-	dur = _region_view->region_relative_distance (timecnt_t ((*_events.begin())->note()->time (), timepos_t()), BeatTime);
-	offset = timecnt_t (_region_view->region()->position(), timepos_t()) + dur;
-
-	_length_clock.set_is_duration (true, pos);
-	_length_clock.set (pos, true, offset);
+	_length_clock.set_duration (timecnt_t ((*_events.begin())->note()->length()), true);
 
 	/* Set up `set all notes...' buttons' sensitivity */
 
diff --git a/gtk2_ardour/editor_drag.cc b/gtk2_ardour/editor_drag.cc
index 48d3ca6fcd..4af0414758 100644
--- a/gtk2_ardour/editor_drag.cc
+++ b/gtk2_ardour/editor_drag.cc
@@ -4333,7 +4333,7 @@ MarkerDrag::start_grab (GdkEvent* event, Gdk::Cursor* cursor)
 		s = min (s, e);
 		e = max (s, e);
 		if (e < timepos_t::max (e.time_domain())) {
-			e.increment();
+			e.increment_by_domain();
 		}
 		_editor->session()->locations()->find_all_between (s, e, ll, Location::Flags (0));
 		for (Locations::LocationList::iterator i = ll.begin(); i != ll.end(); ++i) {
@@ -6632,7 +6632,7 @@ EditorRubberbandSelectDrag::select_things (int button_state, timepos_t const & x
 
 	_editor->begin_reversible_selection_op (X_("rubberband selection"));
 
-	_editor->select_all_within (x1, x2.decrement(), y1, y2, _editor->track_views, op, false);
+	_editor->select_all_within (x1, x2.decrement_by_domain(), y1, y2, _editor->track_views, op, false);
 
 	_editor->commit_reversible_selection_op ();
 }
diff --git a/gtk2_ardour/editor_markers.cc b/gtk2_ardour/editor_markers.cc
index f4cdf6a6f1..092a30979f 100644
--- a/gtk2_ardour/editor_markers.cc
+++ b/gtk2_ardour/editor_markers.cc
@@ -1310,7 +1310,7 @@ Editor::marker_menu_select_all_selectables_using_range ()
 	bool is_start;
 
 	if (((l = find_location_from_marker (marker, is_start)) != 0) && (l->end() > l->start())) {
-		select_all_within (l->start(), l->end().decrement(), 0,  DBL_MAX, track_views, Selection::Set, false);
+		select_all_within (l->start(), l->end(), 0,  DBL_MAX, track_views, Selection::Set, false);
 	}
 
 }
diff --git a/gtk2_ardour/editor_ops.cc b/gtk2_ardour/editor_ops.cc
index f2dd50629c..82639bc66c 100644
--- a/gtk2_ardour/editor_ops.cc
+++ b/gtk2_ardour/editor_ops.cc
@@ -350,7 +350,7 @@ Editor::move_range_selection_start_or_end_to_region_boundary (bool move_end, boo
 
 	/* so we don't find the current region again */
 	if (dir > 0 || pos.is_positive()) {
-		pos = pos.increment ();
+		pos = pos.increment_by_domain ();
 	}
 
 	timepos_t const target = get_region_boundary (pos, dir, true, false);
@@ -835,7 +835,7 @@ Editor::build_region_boundary_cache ()
 			}
 		}
 
-		pos = lpos.increment();
+		pos = lpos.increment_by_domain();
 	}
 
 	/* finally sort to be sure that the order is correct */
@@ -976,7 +976,7 @@ Editor::cursor_to_region_boundary (bool with_selection, int32_t dir)
 
 	// so we don't find the current region again..
 	if (dir > 0 || pos > 0) {
-		pos = pos.increment();
+		pos = pos.increment_by_domain();
 	}
 
 	if ((target = get_region_boundary (pos, dir, with_selection, false)) < 0) {
@@ -1012,7 +1012,7 @@ Editor::cursor_to_region_point (EditorCursor* cursor, RegionPoint point, int32_t
 
 	// so we don't find the current region again..
 	if (dir > 0 || pos.is_positive())
-		pos = pos.increment();
+		pos = pos.increment_by_domain();
 
 	if (!selection->tracks.empty()) {
 
@@ -1155,7 +1155,7 @@ Editor::selected_marker_to_region_boundary (bool with_selection, int32_t dir)
 
 	// so we don't find the current region again..
 	if (dir > 0 || pos.is_positive()) {
-		pos = pos.increment();
+		pos = pos.increment_by_domain();
 	}
 
 	if ((target = get_region_boundary (pos, dir, with_selection, false)) < 0) {
@@ -1199,7 +1199,7 @@ Editor::selected_marker_to_region_point (RegionPoint point, int32_t dir)
 
 	// so we don't find the current region again..
 	if (dir > 0 || pos > 0) {
-		pos = pos.increment();
+		pos = pos.increment_by_domain();
 	}
 
 	if (!selection->tracks.empty()) {
@@ -3428,7 +3428,7 @@ Editor::separate_under_selected_regions ()
 		}
 
 		//Partition on the region bounds
-		playlist->partition ((*rl)->position().decrement(), (*rl)->end(), true);
+		playlist->partition ((*rl)->position().decrement_by_domain(), (*rl)->end(), true);
 
 		//Re-add region that was just removed due to the partition operation
 		playlist->add_region ((*rl), (*rl)->position());
@@ -3553,7 +3553,7 @@ Editor::region_fill_track ()
 
 	timepos_t const end (_session->current_end_sample ());
 
-	if (regions.empty () || regions.end_time().increment() >= end) {
+	if (regions.empty () || regions.end_time().increment_by_domain() >= end) {
 		return;
 	}
 
@@ -3972,7 +3972,8 @@ Editor::trim_to_region(bool forward)
 				continue;
 			}
 
-			region->trim_end (next_region->position().decrement());
+			/* new end is 1 domain unit before the next region */
+			region->trim_end (next_region->position().decrement_by_domain());
 			arv->region_changed (PropertyChange (ARDOUR::Properties::length));
 		}
 		else {
@@ -9634,7 +9635,7 @@ Editor::effective_ripple_mark_start (boost::shared_ptr<Playlist> target_playlist
 	}
 
 	if (last_region_end_before_at < pos) {
-		pos = last_region_end_before_at.increment();
+		pos = last_region_end_before_at.increment_by_domain();
 	}
 #endif
 
diff --git a/gtk2_ardour/editor_selection.cc b/gtk2_ardour/editor_selection.cc
index 0f57542e97..cdcccf8d74 100644
--- a/gtk2_ardour/editor_selection.cc
+++ b/gtk2_ardour/editor_selection.cc
@@ -2186,7 +2186,7 @@ Editor::select_all_selectables_using_edit (bool after, bool from_context_menu)
 	} else {
 		if ((end = get_preferred_edit_position(EDIT_IGNORE_NONE, from_context_menu)) > 1) {
 			start = timepos_t ();
-			end = end.decrement();
+			end = end.decrement_by_domain();
 		} else {
 			return;
 		}
diff --git a/gtk2_ardour/insert_remove_time_dialog.cc b/gtk2_ardour/insert_remove_time_dialog.cc
index 55883cc7ac..89136865d5 100644
--- a/gtk2_ardour/insert_remove_time_dialog.cc
+++ b/gtk2_ardour/insert_remove_time_dialog.cc
@@ -74,14 +74,10 @@ InsertRemoveTimeDialog::InsertRemoveTimeDialog (PublicEditor& e, bool remove)
 
 	//if a Range is selected, assume the user wants to insert/remove the length of the range
 	if ( _editor.get_selection().time.length() != 0 ) {
-		position_clock.set (_editor.get_selection().time.start_time(), true);
-		duration_clock.set (_editor.get_selection().time.end_time(), true,  timecnt_t (_editor.get_selection().time.start_time()));
-		duration_clock.set_bbt_reference (_editor.get_selection().time.start_time());
+		duration_clock.set_duration (_editor.get_selection().time.start_time().distance (_editor.get_selection().time.start_time()), true);
 	} else {
 		timepos_t const pos = _editor.get_preferred_edit_position (EDIT_IGNORE_MOUSE);
-		position_clock.set (pos, true);
-		duration_clock.set_bbt_reference (pos);
-		duration_clock.set (timepos_t());
+		duration_clock.set_duration (timecnt_t (pos));
 	}
 
 	if (!remove) {
diff --git a/gtk2_ardour/main_clock.cc b/gtk2_ardour/main_clock.cc
index 1ffd903ab2..d098240bdb 100644
--- a/gtk2_ardour/main_clock.cc
+++ b/gtk2_ardour/main_clock.cc
@@ -108,7 +108,7 @@ MainClock::absolute_time () const
 }
 
 void
-MainClock::set (timepos_t const & when, bool force, timecnt_t const & /*offset*/)
+MainClock::set (timepos_t const & when, bool force)
 {
 	ClockDeltaMode mode;
 	if (_primary) {
@@ -126,12 +126,12 @@ MainClock::set (timepos_t const & when, bool force, timecnt_t const & /*offset*/
 			AudioClock::set (when, force);
 			break;
 		case DeltaEditPoint:
-			AudioClock::set (when, force, timecnt_t (PublicEditor::instance().get_preferred_edit_position (Editing::EDIT_IGNORE_PHEAD)));
+			AudioClock::set_duration (when.distance (PublicEditor::instance().get_preferred_edit_position (Editing::EDIT_IGNORE_PHEAD)), force);
 			break;
 		case DeltaOriginMarker:
 			{
 				Location* loc = AudioEngine::instance()->session()->locations()->clock_origin_location ();
-				AudioClock::set (when, force, loc ? timecnt_t (loc->start()) : timecnt_t());
+				AudioClock::set_duration (when.distance (loc ? loc->start() : timepos_t (when.time_domain())), force);
 			}
 			break;
 	}
diff --git a/gtk2_ardour/main_clock.h b/gtk2_ardour/main_clock.h
index c8e89fd549..a87ca600c5 100644
--- a/gtk2_ardour/main_clock.h
+++ b/gtk2_ardour/main_clock.h
@@ -31,7 +31,7 @@ public:
 	MainClock (const std::string& clock_name, const std::string& widget_name, bool primary);
 	Temporal::timepos_t absolute_time () const;
 	void set_session (ARDOUR::Session *s);
-	void set (Temporal::timepos_t const &, bool force = false, Temporal::timecnt_t const & offset = Temporal::timecnt_t ());
+	void set (Temporal::timepos_t const &, bool force = false);
 
 private:
 
diff --git a/gtk2_ardour/region_editor.cc b/gtk2_ardour/region_editor.cc
index b7c5f6e717..242e537984 100644
--- a/gtk2_ardour/region_editor.cc
+++ b/gtk2_ardour/region_editor.cc
@@ -334,7 +334,11 @@ RegionEditor::length_clock_changed ()
 		in_command = true;
 
 		_region->clear_changes ();
-		_region->trim_end (_region->position() + len.decrement());
+		/* new end is actually 1 domain unit before the clock duration
+		 * would otherwise indicate
+		 */
+		const timepos_t new_end = (_region->position() + len).decrement_by_domain ();
+		_region->trim_end (new_end);
 		_session->add_command(new StatefulDiffCommand (_region));
 	}
 
diff --git a/gtk2_ardour/region_selection.cc b/gtk2_ardour/region_selection.cc
index 7f3309eade..913d642b3c 100644
--- a/gtk2_ardour/region_selection.cc
+++ b/gtk2_ardour/region_selection.cc
@@ -316,7 +316,7 @@ RegionSelection::end_time () const
 	timepos_t e (timepos_t::zero (front()->region()->position().time_domain()));
 
 	for (RegionSelection::const_iterator i = begin(); i != end(); ++i) {
-		e = max (e, (*i)->region()->end ());
+		e = max (e, (*i)->region()->nt_last ());
 	}
 
 	return e;
diff --git a/gtk2_ardour/region_view.cc b/gtk2_ardour/region_view.cc
index 143d49f019..7f7e43af83 100644
--- a/gtk2_ardour/region_view.cc
+++ b/gtk2_ardour/region_view.cc
@@ -1008,7 +1008,7 @@ RegionView::update_coverage_frame (LayerDisplay d)
 
 	while (t < end) {
 
-		t = t.increment ();
+		t = t.increment_by_domain ();
 
 		/* is this region is on top at time t? */
 		bool const new_me = pl->region_is_audible_at (_region, t);
@@ -1086,7 +1086,7 @@ RegionView::trim_front (timepos_t const & new_bound, bool no_overlap)
 
 		/* Only trim region on the left if the first sample has gone beyond the left region's last sample. */
 		if (region_left && (region_left->nt_last() > _region->position() || regions_touching)) {
-			region_left->trim_end (_region->position().decrement());
+			region_left->trim_end (_region->position().decrement_by_domain());
 		}
 	}
 
@@ -1113,7 +1113,7 @@ RegionView::trim_end (timepos_t const & new_bound, bool no_overlap)
 
 		bool regions_touching = false;
 
-		if (region_right && (last == region_right->position().decrement())) {
+		if (region_right && (last == region_right->position().decrement_by_domain())) {
 			regions_touching = true;
 		}
 
diff --git a/gtk2_ardour/sfdb_ui.cc b/gtk2_ardour/sfdb_ui.cc
index dd50cefa8d..ea3e8eef63 100644
--- a/gtk2_ardour/sfdb_ui.cc
+++ b/gtk2_ardour/sfdb_ui.cc
@@ -218,7 +218,6 @@ SoundFileBox::SoundFileBox (bool /*persistent*/)
 	table.attach (timecode_clock,  1, 2, row, row+1, FILL, FILL);  row+=1;
 	table.attach (tempomap_value,  1, 2, row, row+1, FILL, FILL);  row+=1;
 
-	length_clock.set_is_duration (true, timepos_t());
 	length_clock.set_mode (ARDOUR_UI::instance()->primary_clock->mode());
 	timecode_clock.set_mode (AudioClock::Timecode);
 
@@ -380,7 +379,7 @@ SoundFileBox::setup_labels (const string& filename)
 			}
 		} else {
 			channels_value.set_text ("");
-			length_clock.set (timepos_t());
+			length_clock.set_duration (timecnt_t());
 			tempomap_value.set_text (_("No tempo data"));
 		}
 
@@ -401,7 +400,7 @@ SoundFileBox::setup_labels (const string& filename)
 		samplerate_value.set_text ("");
 		tags_entry.get_buffer()->set_text ("");
 
-		length_clock.set (timepos_t());
+		length_clock.set_duration (timecnt_t());
 		timecode_clock.set (timepos_t());
 
 		tags_entry.set_sensitive (false);
@@ -433,7 +432,6 @@ SoundFileBox::setup_labels (const string& filename)
 	samplecnt_t const nfr = _session ? _session->nominal_sample_rate() : 25;
 	double src_coef = (double) nfr / sf_info.samplerate;
 
-	length_clock.set_is_duration (true, timepos_t());
 	length_clock.set_duration (timecnt_t (samplecnt_t (llrint (sf_info.length * src_coef + 0.5))), true);
 	timecode_clock.set (timepos_t (samplepos_t (llrint (sf_info.timecode * src_coef + 0.5))), true);
 
diff --git a/gtk2_ardour/strip_silence_dialog.cc b/gtk2_ardour/strip_silence_dialog.cc
index 1222e2f2f2..88108ed071 100644
--- a/gtk2_ardour/strip_silence_dialog.cc
+++ b/gtk2_ardour/strip_silence_dialog.cc
@@ -63,9 +63,6 @@ StripSilenceDialog::StripSilenceDialog (Session* s, list<RegionView*> const & v)
 		views.push_back (ViewInterval (*r));
 	}
 
-	_minimum_length->set_is_duration (true, views.front().view->region()->position());
-	_fade_length->set_is_duration (true, views.front().view->region()->position());
-
 	Gtk::HBox* hbox = Gtk::manage (new Gtk::HBox);
 
 	Gtk::Table* table = Gtk::manage (new Gtk::Table (3, 3));
@@ -106,7 +103,6 @@ StripSilenceDialog::StripSilenceDialog (Session* s, list<RegionView*> const & v)
 
 	_fade_length->set_session (s);
 	_fade_length->set_mode (AudioClock::Samples);
-	_fade_length->set_is_duration (true, timepos_t());
 	_fade_length->set_duration (timecnt_t (_fade_length_value), true);
 
 	hbox->pack_start (*table);
diff --git a/gtk2_ardour/time_axis_view.cc b/gtk2_ardour/time_axis_view.cc
index aed370613e..99301ccfda 100644
--- a/gtk2_ardour/time_axis_view.cc
+++ b/gtk2_ardour/time_axis_view.cc
@@ -895,7 +895,7 @@ TimeAxisView::show_selection (TimeSelection& ts)
 		rect = get_selection_rect ((*i).id);
 
 		x1 = _editor.time_to_pixel (start);
-		x2 = _editor.time_to_pixel (end.decrement());
+		x2 = _editor.time_to_pixel (end.decrement_by_domain());
 		y2 = current_height() - 1;
 
 		if (dynamic_cast<AudioTimeAxisView*>(this)) {
diff --git a/gtk2_ardour/time_fx_dialog.cc b/gtk2_ardour/time_fx_dialog.cc
index aa83b5181d..bdd9296442 100644
--- a/gtk2_ardour/time_fx_dialog.cc
+++ b/gtk2_ardour/time_fx_dialog.cc
@@ -148,9 +148,8 @@ TimeFXDialog::TimeFXDialog (Editor& e, bool pitch, timecnt_t const & oldlen, tim
 		vector<string> strings;
 		duration_clock = manage (new AudioClock (X_("stretch"), true, X_("stretch"), true, false, true, false, true));
 		duration_clock->set_session (e.session());
-		duration_clock->set (timepos_t (new_length), true);
 		duration_clock->set_mode (AudioClock::BBT);
-		duration_clock->set_bbt_reference (position);
+		duration_clock->set_duration (timecnt_t (new_length, position));
 
 		Gtk::Alignment* clock_align = manage (new Gtk::Alignment);
 		clock_align->add (*duration_clock);
diff --git a/gtk2_ardour/time_info_box.cc b/gtk2_ardour/time_info_box.cc
index df472e28e0..82c47b4a19 100644
--- a/gtk2_ardour/time_info_box.cc
+++ b/gtk2_ardour/time_info_box.cc
@@ -242,8 +242,8 @@ TimeInfoBox::region_selection_changed ()
 	selection_end->set_off (false);
 	selection_length->set_off (false);
 	selection_start->set (s);
-	selection_end->set (e);
-	selection_length->set_duration (timecnt_t (e), false, timecnt_t (s));
+	selection_end->set (e.decrement_by_domain());
+	selection_length->set_duration (s.distance (e), true);
 }
 
 void
@@ -273,8 +273,7 @@ TimeInfoBox::selection_changed ()
 					selection_end->set_off (false);
 					selection_length->set_off (false);
 					selection_start->set (selection.time.start_time());
-					selection_end->set (selection.time.end_time());
-					selection_length->set_is_duration (true, selection.time.start_time());
+					selection_end->set (selection.time.end_time().decrement_by_domain());
 					selection_length->set_duration (selection.time.start_time().distance (selection.time.end_time()));
 				} else {
 					selection_start->set_off (true);
@@ -293,9 +292,8 @@ TimeInfoBox::selection_changed ()
 				selection_end->set_off (false);
 				selection_length->set_off (false);
 				selection_start->set (s);
-				selection_end->set (e);
-				selection_length->set_is_duration (true, s);
-				selection_length->set (e, false, timecnt_t (s));
+				selection_end->set (e.decrement_by_domain());
+				selection_length->set_duration (s.distance (e), false);
 			}
 		} else {
 			/* this is more efficient than tracking changes per region in large selections */
@@ -326,9 +324,8 @@ TimeInfoBox::selection_changed ()
 				selection_end->set_off (false);
 				selection_length->set_off (false);
 				selection_start->set (s);
-				selection_end->set (e);
-				selection_length->set_is_duration (true, s);
-				selection_length->set (e, false, timecnt_t (s));
+				selection_end->set (e.decrement_by_domain());
+				selection_length->set_duration(s.distance (e));
 			} else {
 				selection_start->set_off (true);
 				selection_end->set_off (true);
@@ -339,9 +336,8 @@ TimeInfoBox::selection_changed ()
 			selection_end->set_off (false);
 			selection_length->set_off (false);
 			selection_start->set (selection.time.start_time());
-			selection_end->set (selection.time.end_time());
-			selection_length->set_is_duration (true, selection.time.start_time());
-			selection_length->set_duration (selection.time.start_time().distance (selection.time.end_time()));
+			selection_end->set (selection.time.end_time().decrement_by_domain());
+			selection_length->set_duration (selection.time.length());
 		}
 		break;