diff --git a/src/depot_base.h b/src/depot_base.h
--- a/src/depot_base.h
+++ b/src/depot_base.h
@@ -12,6 +12,7 @@
 
 #include "depot_map.h"
 #include "core/pool_type.hpp"
+#include "timer/timer_game_calendar.h"
 
 typedef Pool<Depot, DepotID, 64, 64000> DepotPool;
 extern DepotPool _depot_pool;
@@ -21,8 +22,8 @@ struct Depot : DepotPool::PoolItem<&_dep
 	std::string name;
 
 	TileIndex xy;
-	uint16 town_cn;    ///< The N-1th depot for this town (consecutive number)
-	Date build_date;   ///< Date of construction
+	uint16 town_cn; ///< The N-1th depot for this town (consecutive number)
+	TimerGameCalendar::Date build_date; ///< Date of construction
 
 	Depot(TileIndex xy = INVALID_TILE) : xy(xy) {}
 	~Depot();