diff --git a/src/mixer/Memento.hxx b/src/mixer/Memento.hxx
index 9fa44e8a8..d862763cd 100644
--- a/src/mixer/Memento.hxx
+++ b/src/mixer/Memento.hxx
@@ -3,7 +3,7 @@
 
 #pragma once
 
-#include "system/PeriodClock.hxx"
+#include "time/PeriodClock.hxx"
 
 class MultipleOutputs;
 class BufferedOutputStream;
diff --git a/src/output/Control.hxx b/src/output/Control.hxx
index eb07dccdb..761068021 100644
--- a/src/output/Control.hxx
+++ b/src/output/Control.hxx
@@ -9,7 +9,7 @@
 #include "thread/Thread.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
-#include "system/PeriodClock.hxx"
+#include "time/PeriodClock.hxx"
 
 #include <cstdint>
 #include <exception>
diff --git a/src/output/plugins/AlsaOutputPlugin.cxx b/src/output/plugins/AlsaOutputPlugin.cxx
index 6f1c6be1f..3e3a6beb4 100644
--- a/src/output/plugins/AlsaOutputPlugin.cxx
+++ b/src/output/plugins/AlsaOutputPlugin.cxx
@@ -15,7 +15,7 @@
 #include "../Error.hxx"
 #include "mixer/plugins/AlsaMixerPlugin.hxx"
 #include "pcm/Export.hxx"
-#include "system/PeriodClock.hxx"
+#include "time/PeriodClock.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
 #include "util/Manual.hxx"
diff --git a/src/system/PeriodClock.hxx b/src/time/PeriodClock.hxx
similarity index 100%
rename from src/system/PeriodClock.hxx
rename to src/time/PeriodClock.hxx