1 /* $Id$ */

     2 

     3 /** @file date.h */

     4 

     5 #ifndef DATE_H

     6 #define DATE_H

     7 

     8 #include "openttd.h"

     9 

    10 /**

    11  * 1 day is 74 ticks; _date_fract used to be uint16 and incremented by 885. On

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

    13  * 1 tick is approximately 30 ms.

    14  * 1 day is thus about 2 seconds (74 * 30 = 2220) on a machine that can run OpenTTD normally

    15  */

    16 #define DAY_TICKS 74

    17 

    18 /*

    19  * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are

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

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

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

    23  */

    24 

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

    26 #define ORIGINAL_BASE_YEAR 1920

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

    28 #define ORIGINAL_MAX_YEAR 2090

    29 

    30 /**

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

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

    33  */

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

    35 

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

    37 #define MIN_YEAR 0

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

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

    40 #define MAX_YEAR 5000000

    41 

    42 /* Year and Date are defined elsewhere */

    43 typedef uint8  Month;

    44 typedef uint8  Day;

    45 typedef uint16 DateFract;

    46 

    47 struct YearMonthDay {

    48 	Year  year;

    49 	Month month;

    50 	Day   day;

    51 };

    52 

    53 extern Year      _cur_year;

    54 extern Month     _cur_month;

    55 extern Date      _date;

    56 extern DateFract _date_fract;

    57 

    58 

    59 void SetDate(Date date);

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

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

    62 

    63 #endif /* DATE_H */