diff --git a/src/currency.h b/src/currency.h
--- a/src/currency.h
+++ b/src/currency.h
@@ -10,7 +10,7 @@
 #ifndef CURRENCY_H
 #define CURRENCY_H
 
-#include "date_type.h"
+#include "timer/timer_game_calendar.h"
 #include "string_func.h"
 #include "strings_type.h"
 
@@ -72,7 +72,7 @@ enum Currencies {
 struct CurrencySpec {
 	uint16 rate;           ///< The conversion rate compared to the base currency.
 	std::string separator; ///< The thousands separator for this currency.
-	Year to_euro;          ///< %Year of switching to the Euro. May also be #CF_NOEURO or #CF_ISEURO.
+	TimerGameCalendar::Year to_euro; ///< Year of switching to the Euro. May also be #CF_NOEURO or #CF_ISEURO.
 	std::string prefix;    ///< Prefix to apply when formatting money in this currency.
 	std::string suffix;    ///< Suffix to apply when formatting money in this currency.
 	/**
@@ -89,7 +89,7 @@ struct CurrencySpec {
 
 	CurrencySpec() = default;
 
-	CurrencySpec(uint16 rate, const char *separator, Year to_euro, const char *prefix, const char *suffix, byte symbol_pos, StringID name) :
+	CurrencySpec(uint16 rate, const char *separator, TimerGameCalendar::Year to_euro, const char *prefix, const char *suffix, byte symbol_pos, StringID name) :
 		rate(rate), separator(separator), to_euro(to_euro), prefix(prefix), suffix(suffix), symbol_pos(symbol_pos), name(name)
 	{
 	}