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/* $Id$ */

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#ifndef DATE_H

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#define DATE_H

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/**

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

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

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 * 1 tick is approximately 30 ms.

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

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 */

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#define DAY_TICKS 74

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/*

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 * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are

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

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

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

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 */

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

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#define ORIGINAL_BASE_YEAR 1920

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

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#define ORIGINAL_MAX_YEAR 2090

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/**

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

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 * 'ConvertYMDToDate(ORIGINAL_BASE_YEAR, 0, 1)'

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 */

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

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

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#define MIN_YEAR 0

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

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

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#define MAX_YEAR 5000000

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/* Year and Date are defined elsewhere */

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typedef uint8  Month;

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typedef uint8  Day;

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typedef uint16 DateFract;

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typedef struct YearMonthDay {

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	Year  year;

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	Month month;

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	Day   day;

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} YearMonthDay;

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extern Year      _cur_year;

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extern Month     _cur_month;

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extern Date      _date;

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extern DateFract _date_fract;

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void SetDate(Date date);

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void ConvertDateToYMD(Date date, YearMonthDay *ymd);

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

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#endif /* DATE_H */