Codechange: move all date-related variables inside the timer (#10706)

src/date_func.h

@@ -12,13 +12,8 @@
 
 #include "date_type.h"
 
-extern Year      _cur_year;
-extern Month     _cur_month;
-extern Date      _date;
-extern DateFract _date_fract;
 extern uint64 _tick_counter;
 
-void SetDate(Date date, DateFract fract);
 void ConvertDateToYMD(Date date, YearMonthDay *ymd);
 Date ConvertYMDToDate(Year year, Month month, Day day);