diff --git a/ext/tk/sample/24hr_clock.rb b/ext/tk/sample/24hr_clock.rb
new file mode 100644
index 0000000000..60d8072c57
--- /dev/null
+++ b/ext/tk/sample/24hr_clock.rb
@@ -0,0 +1,286 @@
+#!/usr/bin/env ruby
+
+require 'tk'
+
+class Clock
+  def initialize(clock24 = true)
+    @clock = (clock24)? 24: 12
+
+    @size = 200
+    @cdot_size = 5
+
+    @cdot_color        = 'black'
+    @hour_hand_color   = 'black'
+    @minute_hand_color = 'gray25'
+    @second_hand_color = 'gray50'
+
+    @mark_font     = 'Helvetica -14'
+    @mark_width    = 3
+    @mark_color    = 'black'
+    @submark_color = 'gray50'
+
+    @c = TkCanvas.new(:width=>2*@size, :height=>2*@size, 
+                     :scrollregion=>[-@size, -@size, @size, @size]
+                     ).pack(:fill=>:both, :expand=>true)
+
+    @tag = TkcTag.new(@c)
+    @hand_tag = TkcTag.new(@c)
+
+    @circle_coords = [[-0.9*@size, -0.9*@size], [0.9*@size, 0.9*@size]]
+    @oval = TkcOval.new(@c, @circle_coords, :fill=>'white', :tags=>[@tag])
+
+    f = TkFrame.new.pack
+    TkLabel.new(f, :text=>'CURRENT:').pack(:side=>:left)
+    @now = TkLabel.new(f, :text=>'00:00:00').pack(:side=>:left, :padx=>2)
+    TkLabel.new(f, :text=>'  ').pack(:side=>:left)
+    TkLabel.new(f, :text=>'  ').pack(:side=>:right)
+    @l = TkLabel.new(f, :text=>'00:00').pack(:side=>:right, :padx=>2)
+    TkLabel.new(f, :text=>'MOUSE-POINTER:').pack(:side=>:right)
+
+    cmd = proc{|x, y|
+      @l.text = '%02d:%02d' % coords_to_time(@c.canvasx(x), @c.canvasy(y))
+    }
+    @c.bind('Motion', cmd, '%x %y')
+    @tag.bind('Motion', cmd, '%x %y')
+
+    _create_hands
+    _create_marks
+
+    timer_proc = proc{
+      t = Time.now
+      @now.text = '%02d:%02d:%02d' % [t.hour, t.min, t.sec]
+      set_hands(t.hour, t.min, t.sec)
+    }
+
+    timer_proc.call
+    @timer = TkRTTimer.start(100, -1, timer_proc)
+  end
+
+  def _create_marks
+    @mark_tag = TkcTag.new(@c)
+
+    TkcLine.new(@c, 0, -0.90*@size, 0, -0.85*@size, 
+                :tags=>[@tag, @mark_tag], 
+                :width=>@mark_width, :fill=>@mark_color)
+    TkcLine.new(@c, 0.90*@size, 0, 0.85*@size, 0, 
+                :tags=>[@tag, @mark_tag], 
+                :width=>@mark_width, :fill=>@mark_color)
+    TkcLine.new(@c, 0, 0.90*@size, 0, 0.85*@size, 
+                :tags=>[@tag, @mark_tag], 
+                :width=>@mark_width, :fill=>@mark_color)
+    TkcLine.new(@c, -0.90*@size, 0, -0.85*@size, 0, 
+                :tags=>[@tag, @mark_tag], 
+                :width=>@mark_width, :fill=>@mark_color)
+
+    TkcText.new(@c, [0, -0.92*@size], :text=>0, 
+                :anchor=>'s', :fill=>@mark_color)
+    TkcText.new(@c, [0.92*@size, 0], :text=>@clock.div(4), 
+                :anchor=>'w', :fill=>@mark_color)
+    TkcText.new(@c, [0, 0.92*@size], :text=>@clock.div(2), 
+                :anchor=>'n', :fill=>@mark_color)
+    TkcText.new(@c, [-0.92*@size, 0], :text=>@clock.div(4)*3, 
+                :anchor=>'e', :fill=>@mark_color)
+
+    [30.0, 60.0].each{|angle|
+      rad = Math::PI * angle / 180.0
+      x_base = @size*Math::sin(rad)
+      y_base = @size*Math::cos(rad)
+
+      x1 = 0.90*x_base
+      y1 = 0.90*y_base
+
+      x2 = 0.85*x_base
+      y2 = 0.85*y_base
+
+      TkcLine.new(@c, x1, y1, x2, y2, 
+                  :tags=>[@tag, @mark_tag], 
+                  :width=>@mark_width, :fill=>@mark_color)
+      TkcLine.new(@c, x1, -y1, x2, -y2, 
+                  :tags=>[@tag, @mark_tag], 
+                  :width=>@mark_width, :fill=>@mark_color)
+      TkcLine.new(@c, -x1, y1, -x2, y2, 
+                  :tags=>[@tag, @mark_tag], 
+                  :width=>@mark_width, :fill=>@mark_color)
+      TkcLine.new(@c, -x1, -y1, -x2, -y2, 
+                  :tags=>[@tag, @mark_tag], 
+                  :width=>@mark_width, :fill=>@mark_color)
+
+      x3 = 0.92*x_base
+      y3 = 0.92*y_base
+
+      if @clock == 24
+        dh = angle.to_i/15
+      else # @clock == 12
+        dh = angle.to_i/30
+      end
+
+      TkcText.new(@c, x3, -y3, :text=>dh, 
+                  :anchor=>'sw', :fill=>@mark_color)
+      TkcText.new(@c, x3, y3, :text=>@clock.div(2)-dh, 
+                  :anchor=>'nw', :fill=>@mark_color)
+      TkcText.new(@c, -x3, y3, :text=>@clock.div(2)+dh, 
+                  :anchor=>'ne', :fill=>@mark_color)
+      TkcText.new(@c, -x3, -y3, :text=>@clock-dh, 
+                  :anchor=>'se', :fill=>@mark_color)
+    }
+
+    if @clock == 24
+      [15.0, 45.0, 75.0].each{|angle|
+        rad = Math::PI * angle / 180.0
+        x_base = @size*Math::sin(rad)
+        y_base = @size*Math::cos(rad)
+
+        x1 = 0.90*x_base
+        y1 = 0.90*y_base
+
+        x2 = 0.875*x_base
+        y2 = 0.875*y_base
+
+        TkcLine.new(@c, x1, y1, x2, y2, 
+                    :tags=>[@tag, @mark_tag], 
+                    :width=>@mark_width, :fill=>@submark_color)
+        TkcLine.new(@c, x1, -y1, x2, -y2, 
+                    :tags=>[@tag, @mark_tag], 
+                    :width=>@mark_width, :fill=>@submark_color)
+        TkcLine.new(@c, -x1, y1, -x2, y2, 
+                    :tags=>[@tag, @mark_tag], 
+                    :width=>@mark_width, :fill=>@submark_color)
+        TkcLine.new(@c, -x1, -y1, -x2, -y2, 
+                    :tags=>[@tag, @mark_tag], 
+                    :width=>@mark_width, :fill=>@submark_color)
+      }
+    end
+  end
+
+  def _create_hands
+    hour_hand_len   = 0.55*@size
+    minute_hand_len = 0.85*@size
+    second_hand_len = 0.88*@size
+
+    hour_hand_width   = 1.8*@cdot_size
+    minute_hand_width = 1.0*@cdot_size
+    second_hand_width = 1 # 0.4*@cdot_size
+
+    @hour_hand_coords = [
+      [0, -0.5*@cdot_size], 
+      [hour_hand_width, -0.5*@cdot_size-hour_hand_width], 
+      [hour_hand_width, -hour_hand_len+hour_hand_width], 
+      [0, -hour_hand_len], 
+      [-hour_hand_width, -hour_hand_len+hour_hand_width], 
+      [-hour_hand_width, -0.5*@cdot_size-hour_hand_width], 
+    ]
+    @minute_hand_coords = [
+      [0, -0.5*@cdot_size], 
+      [minute_hand_width, -0.5*@cdot_size - minute_hand_width], 
+      [minute_hand_width, -minute_hand_len+minute_hand_width], 
+      [0, -minute_hand_len], 
+      [-minute_hand_width, -minute_hand_len+minute_hand_width], 
+      [-minute_hand_width, -0.5*@cdot_size-minute_hand_width], 
+    ]
+    @second_hand_coords = [
+      [0, -0.5*@cdot_size], 
+      [second_hand_width, -0.5*@cdot_size - second_hand_width], 
+      [second_hand_width, -second_hand_len+second_hand_width], 
+      [0, -second_hand_len], 
+      [-second_hand_width, -second_hand_len+second_hand_width], 
+      [-second_hand_width, -0.5*@cdot_size-second_hand_width], 
+    ]
+
+    @hour_hand = TkcPolygon.new(@c, @hour_hand_coords, 
+                                :tags=>[@tag, @hand_tag], 
+                                :outline=>@hour_hand_color, 
+                                :fill=>@hour_hand_color)
+
+    @minute_hand = TkcPolygon.new(@c, @minute_hand_coords, 
+                                  :tags=>[@tag, @hand_tag], 
+                                  :outline=>@minute_hand_color, 
+                                  :fill=>@minute_hand_color)
+
+    @second_hand = TkcPolygon.new(@c, @second_hand_coords, 
+                                  :tags=>[@tag, @hand_tag], 
+                                  :outline=>@second_hand_color, 
+                                  :fill=>@second_hand_color)
+
+    @center_dot = TkcOval.new(@c, 
+                              [-@cdot_size, -@cdot_size], 
+                              [@cdot_size, @cdot_size], 
+                              :outline=>@cdot_color, :fill=>@cdot_color)
+  end
+  private :_create_hands
+
+  def _raise_hands
+    @hour_hand.raise
+    @minute_hand.raise
+    @second_hand.raise
+    @center_dot.raise
+  end
+  private :_raise_hands
+
+  def _raise_marks
+    @mark_tag.raise
+  end
+  private :_raise_marks
+
+  def set_hands(hh, mm, ss)
+    ss_angle = Math::PI * ss / 30.0
+    mm_angle = Math::PI * (mm + ss/60.0) / 30.0
+    hh_angle = Math::PI * (hh + (mm + ss/60.0)/60.0) / (@clock.div(2))
+
+    @second_hand.coords = @second_hand_coords.collect{|x, y|
+      r = Math::hypot(y, x)
+      a = Math::atan2(y, x) + ss_angle
+      [Math::cos(a) * r, Math::sin(a) * r]
+    }
+
+    @minute_hand.coords = @minute_hand_coords.collect{|x, y|
+      r = Math::hypot(y, x)
+      a = Math::atan2(y, x) + mm_angle
+      [Math::cos(a) * r, Math::sin(a) * r]
+    }
+
+    @hour_hand.coords = @hour_hand_coords.collect{|x, y|
+      r = Math::hypot(y, x)
+      a = Math::atan2(y, x) + hh_angle
+      [Math::cos(a) * r, Math::sin(a) * r]
+    }
+
+    _raise_hands
+    _raise_marks
+  end
+
+  def coords_to_time(x, y)
+    return ((y < 0)? [0, 0]: [@clock.div(2), 0])  if x == 0
+    if @clock == 24
+      offset = (x<0&&y<0)? 1800.0: 360.0
+      m_half = 720.0
+    else # @clock == 12
+      offset = (x<0&&y<0)? 900.0: 180.0
+      m_half = 360.0
+    end
+    (offset + m_half*Math.atan2(y,x)/Math::PI).round.divmod(60)
+  end
+
+  def create_pie(hh, mm, span, color='red')
+    if @clock == 24
+      start  = 90.0 - (hh*60 + mm)/4.0  # 360.0*(hh*60+mm)/(24*60)
+      extent = -span/4.0
+    else # @clock == 12
+      start  = 90.0 - (hh*60 + mm)/2.0  # 360.0*(hh*60+mm)/(12*60)
+      extent = -span/2.0
+    end
+
+    pie = TkcArc.new(@c, @circle_coords, :tags=>[@tag], 
+                     :outline=>'black', 'fill'=>color, 
+                     :start=>start, :extent=>extent)
+    _raise_hands
+    _raise_marks
+    pie
+  end
+end
+
+sched = Clock.new
+sched.create_pie(0,0, 60)            #  60 minutes from 00:00
+sched.create_pie(6,30, 280, 'green') # 280 minutes from 06:30
+sched.create_pie(15,20, 90, 'blue')  #  90 minutes from 15:20
+
+Tk.mainloop