1 /* $Id$ */

     2 

     3 #ifndef DATE_H

     4 #define DATE_H

     5 

     6 #include "openttd.h"

     7 

     8 /**

     9  * 1 day is 74 ticks; _date_fract used to be uint16 and incremented by 885. On

    10  *                    an overflow the new day begun and 65535 / 885 = 74.

    11  * 1 tick is approximately 30 ms.

    12  * 1 day is thus about 2 seconds (74 * 30 = 2220) on a machine that can run OpenTTD normally

    13  */

    14 #define DAY_TICKS 74

    15 

    16 /*

    17  * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are

    18  * primarily used for loading newgrf and savegame data and returning some

    19  * newgrf (callback) functions that were in the original (TTD) inherited

    20  * format, where '_date == 0' meant that it was 1920-01-01.

    21  */

    22 

    23 /** The minimum starting year/base year of the original TTD */

    24 #define ORIGINAL_BASE_YEAR 1920

    25 /** The maximum year of the original TTD */

    26 #define ORIGINAL_MAX_YEAR 2090

    27 

    28 /**

    29  * The offset in days from the '_date == 0' till

    30  * 'ConvertYMDToDate(ORIGINAL_BASE_YEAR, 0, 1)'

    31  */

    32 #define DAYS_TILL_ORIGINAL_BASE_YEAR (365 * ORIGINAL_BASE_YEAR + ORIGINAL_BASE_YEAR / 4 - ORIGINAL_BASE_YEAR / 100 + ORIGINAL_BASE_YEAR / 400)

    33 

    34 /* The absolute minimum & maximum years in OTTD */

    35 #define MIN_YEAR 0

    36 /* MAX_YEAR, nicely rounded value of the number of years that can

    37  * be encoded in a single 32 bits date, about 2^31 / 366 years. */

    38 #define MAX_YEAR 5000000

    39 

    40 /* Year and Date are defined elsewhere */

    41 typedef uint8  Month;

    42 typedef uint8  Day;

    43 typedef uint16 DateFract;

    44 

    45 typedef struct YearMonthDay {

    46 	Year  year;

    47 	Month month;

    48 	Day   day;

    49 } YearMonthDay;

    50 

    51 extern Year      _cur_year;

    52 extern Month     _cur_month;

    53 extern Date      _date;

    54 extern DateFract _date_fract;

    55 

    56 

    57 void SetDate(Date date);

    58 void ConvertDateToYMD(Date date, YearMonthDay *ymd);

    59 Date ConvertYMDToDate(Year year, Month month, Day day);

    60 

    61 #endif /* DATE_H */