diff --git a/src/date.cpp b/src/date.cpp
--- a/src/date.cpp
+++ b/src/date.cpp
@@ -26,7 +26,7 @@ Year      _cur_year;   ///< Current year
 Month     _cur_month;  ///< Current month (0..11)
 Date      _date;       ///< Current date in days (day counter)
 DateFract _date_fract;
-
+uint16 _tick_counter;  ///< Ever incrementing (and sometimes wrapping) tick counter for setting off various events
 
 void SetDate(Date date)
 {
diff --git a/src/date_func.h b/src/date_func.h
--- a/src/date_func.h
+++ b/src/date_func.h
@@ -18,6 +18,7 @@ extern Year      _cur_year;
 extern Month     _cur_month;
 extern Date      _date;
 extern DateFract _date_fract;
+extern uint16 _tick_counter;
 
 void SetDate(Date date);
 void ConvertDateToYMD(Date date, YearMonthDay *ymd);
diff --git a/src/gamelog.cpp b/src/gamelog.cpp
--- a/src/gamelog.cpp
+++ b/src/gamelog.cpp
@@ -19,6 +19,7 @@
 #include "gamelog_internal.h"
 #include "console_func.h"
 #include "debug.h"
+#include "date_func.h"
 #include "rev.h"
 
 #include <stdarg.h>
diff --git a/src/newgrf_airporttiles.cpp b/src/newgrf_airporttiles.cpp
--- a/src/newgrf_airporttiles.cpp
+++ b/src/newgrf_airporttiles.cpp
@@ -28,6 +28,7 @@
 #include "core/random_func.hpp"
 #include "table/strings.h"
 #include "table/airporttiles.h"
+#include "date_func.h"
 
 
 AirportTileSpec AirportTileSpec::tiles[NUM_AIRPORTTILES];
diff --git a/src/newgrf_house.cpp b/src/newgrf_house.cpp
--- a/src/newgrf_house.cpp
+++ b/src/newgrf_house.cpp
@@ -28,6 +28,7 @@
 #include "core/random_func.hpp"
 #include "sprite.h"
 #include "genworld.h"
+#include "date_func.h"
 
 static BuildingCounts<uint32> _building_counts;
 static HouseClassMapping _class_mapping[HOUSE_CLASS_MAX];
diff --git a/src/newgrf_industrytiles.cpp b/src/newgrf_industrytiles.cpp
--- a/src/newgrf_industrytiles.cpp
+++ b/src/newgrf_industrytiles.cpp
@@ -27,6 +27,7 @@
 #include "animated_tile_func.h"
 #include "water.h"
 #include "sprite.h"
+#include "date_func.h"
 
 #include "table/strings.h"
 
diff --git a/src/variables.h b/src/variables.h
--- a/src/variables.h
+++ b/src/variables.h
@@ -16,7 +16,4 @@
 #define VARDEF extern
 #endif
 
-/* Amount of game ticks */
-VARDEF uint16 _tick_counter;
-
 #endif /* VARIABLES_H */