diff --git a/Game.h b/Game.h
index c6ebe8b..a44c41b 100644
--- a/Game.h
+++ b/Game.h
@@ -6,6 +6,8 @@
 #include "iDrawable.h"
 #include "iWritable.h"
 #include "Logger.h"
+#include "OffsetClock.h"
+#include "SystemClock.h"
 #include "Texture.h"
 
 
@@ -22,7 +24,8 @@ class Game : public iDrawable, public iWritable {
   Game& operator=(const Game&) = delete;
 
   Game(iAllocator* alloc, uint32_t w, uint32_t h) :
-      alloc_(alloc), w_(w), h_(h), logger_(h), test_(Colorbuffer(alloc, 1, 1)) {
+      alloc_(alloc), uptime_(&SystemClock::instance()),
+      w_(w), h_(h), logger_(h), test_(Colorbuffer(alloc, 1, 1)) {
     Colorbuffer temp(alloc_, 5, 5);
     float* ptr = temp.ptr();
     for (size_t i = 0; i < 25; ++i) ptr[i] = i%2*.3+.7;
@@ -30,11 +33,10 @@ class Game : public iDrawable, public iWritable {
   }
 
   void Update() {
-    static int i = 0;
-    ++i;
-    if (i%100 == 0) logger_.Print(L"すべての人類は死滅する: "+std::to_wstring(i));
+    const uint64_t i = uptime_.now();
+    if (i%1000 == 0) logger_.Print(L"すべての人類は死滅する: "+std::to_wstring(i));
 
-    double t = i%200/200.;
+    double t = i%2000/2000.;
     t = 1 - t;
 
     mat3 m = mat3{ {.2, 0, 0},{0, .2, 0},{0, 0, 1} };
@@ -55,6 +57,7 @@ class Game : public iDrawable, public iWritable {
 
  private:
   iAllocator* alloc_;
+  OffsetClock uptime_;
 
   uint32_t w_, h_;
   Logger logger_;
diff --git a/GlyphsJuke.vcxproj b/GlyphsJuke.vcxproj
index 627fec8..1b66d8c 100644
--- a/GlyphsJuke.vcxproj
+++ b/GlyphsJuke.vcxproj
@@ -150,13 +150,16 @@
     <ClInclude Include="Game.h" />
     <ClInclude Include="iDrawable.h" />
     <ClInclude Include="iLogger.h" />
+    <ClInclude Include="iClock.h" />
     <ClInclude Include="iWritable.h" />
     <ClInclude Include="Logger.h" />
+    <ClInclude Include="OffsetClock.h" />
     <ClInclude Include="Rasterbuffer.h" />
     <ClInclude Include="iConsole.h" />
     <ClInclude Include="iAllocator.h" />
     <ClInclude Include="LinearAllocator.h" />
     <ClInclude Include="StackAllocator.h" />
+    <ClInclude Include="SystemClock.h" />
     <ClInclude Include="Text.h" />
     <ClInclude Include="Texture.h" />
     <ClInclude Include="thirdparty\linalg.h" />
diff --git a/GlyphsJuke.vcxproj.filters b/GlyphsJuke.vcxproj.filters
index f74e228..ec2bd0b 100644
--- a/GlyphsJuke.vcxproj.filters
+++ b/GlyphsJuke.vcxproj.filters
@@ -80,5 +80,14 @@
     <ClInclude Include="Texture.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="iClock.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="SystemClock.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
+    <ClInclude Include="OffsetClock.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/OffsetClock.h b/OffsetClock.h
new file mode 100644
index 0000000..794870b
--- /dev/null
+++ b/OffsetClock.h
@@ -0,0 +1,38 @@
+#pragma once
+
+#include <cstdint>
+
+#define NOMINMAX
+#include <windows.h>
+#undef NOMINMAX
+
+#include "iClock.h"
+
+namespace gj {
+
+
+class OffsetClock : public iClock {
+ public:
+  OffsetClock(OffsetClock&&) = default;
+  OffsetClock(const OffsetClock&) = default;
+
+  OffsetClock& operator=(OffsetClock&&) = default;
+  OffsetClock& operator=(const OffsetClock&) = default;
+
+  OffsetClock(const iClock* parent, uint64_t offset) :
+      parent_(parent), offset_(offset) {
+  }
+  OffsetClock(const iClock* parent) : OffsetClock(parent, parent->now()) {
+  }
+
+  uint64_t now() const override {
+    return parent_->now() - offset_;
+  }
+
+ private:
+  const iClock* parent_;
+  uint64_t      offset_;
+};
+
+
+}
\ No newline at end of file
diff --git a/SystemClock.h b/SystemClock.h
new file mode 100644
index 0000000..46a51ff
--- /dev/null
+++ b/SystemClock.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <cstdint>
+
+#define NOMINMAX
+#include <windows.h>
+#undef NOMINMAX
+
+#include "iClock.h"
+
+
+namespace gj {
+
+
+class SystemClock : public iClock {
+ public:
+  static const SystemClock& instance() {
+    static const SystemClock instance_;
+    return instance_;
+  }
+
+  SystemClock() = default;
+  SystemClock(SystemClock&&) = default;
+  SystemClock(const SystemClock&) = default;
+
+  SystemClock& operator=(SystemClock&&) = default;
+  SystemClock& operator=(const SystemClock&) = default;
+
+  uint64_t now() const override {
+    return GetTickCount64();
+  }
+};
+
+
+}
\ No newline at end of file
diff --git a/iClock.h b/iClock.h
new file mode 100644
index 0000000..8ee1cc7
--- /dev/null
+++ b/iClock.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include <cstdint>
+
+
+namespace gj {
+
+
+class iClock {
+ public:
+  iClock() = default;
+  iClock(iClock&&) = default;
+  iClock(const iClock&) = default;
+
+  iClock& operator=(iClock&&) = default;
+  iClock& operator=(const iClock&) = default;
+
+  virtual ~iClock() = default;
+
+  virtual uint64_t now() const = 0;
+};
+
+
+
+}
\ No newline at end of file