diff --git a/src/script/api/script_basestation.cpp b/src/script/api/script_basestation.cpp
--- a/src/script/api/script_basestation.cpp
+++ b/src/script/api/script_basestation.cpp
@@ -15,6 +15,7 @@
 #include "../../strings_func.h"
 #include "../../station_cmd.h"
 #include "../../waypoint_cmd.h"
+#include "../../timer/timer_game_calendar.h"
 #include "table/strings.h"
 
 #include "../../safeguards.h"
diff --git a/src/script/api/script_date.hpp b/src/script/api/script_date.hpp
--- a/src/script/api/script_date.hpp
+++ b/src/script/api/script_date.hpp
@@ -11,7 +11,7 @@
 #define SCRIPT_DATE_HPP
 
 #include "script_object.hpp"
-#include "timer/timer_game_calendar.h"
+#include "../../timer/timer_game_calendar.h"
 
 /**
  * Class that handles all date related (calculation) functions.
diff --git a/src/script/api/script_engine.cpp b/src/script/api/script_engine.cpp
--- a/src/script/api/script_engine.cpp
+++ b/src/script/api/script_engine.cpp
@@ -18,6 +18,7 @@
 #include "../../engine_func.h"
 #include "../../articulated_vehicles.h"
 #include "../../engine_cmd.h"
+#include "../../timer/timer_game_calendar.h"
 #include "table/strings.h"
 
 #include "../../safeguards.h"