static const int DAYS_IN_YEAR      = 365; ///< days per year

static const int DAYS_IN_LEAP_YEAR = 366; ///< sometimes, you need one day more...

static const int MONTHS_IN_YEAR    =  12; ///< months per year

static const int SECONDS_PER_DAY   = 2;   ///< approximate seconds per day, not for precise calculations

/*

 * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are

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

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

 * format, where 'TimerGameCalendar::date == 0' meant that it was 1920-01-01.

 */

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

static constexpr TimerGameCalendar::Year ORIGINAL_BASE_YEAR = 1920;

/** The original ending year */

static constexpr TimerGameCalendar::Year ORIGINAL_END_YEAR = 2051;

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

static constexpr TimerGameCalendar::Year ORIGINAL_MAX_YEAR = 2090;

/**

 * Calculate the date of the first day of a given year.

 * @param year the year to get the first day of.

 * @return the date.

 */

static constexpr TimerGameCalendar::Date DateAtStartOfYear(TimerGameCalendar::Year year)

{

	int32_t year_as_int = static_cast<int32_t>(year);

	uint number_of_leap_years = (year == 0) ? 0 : ((year_as_int - 1) / 4 - (year_as_int - 1) / 100 + (year_as_int - 1) / 400 + 1);

	return (DAYS_IN_YEAR * year_as_int) + number_of_leap_years;

}

/**

 * Calculate the year of a given date.

 * @param date The date to consider.

 * @return the year.

 */

static inline TimerGameCalendar::Year DateToYear(TimerGameCalendar::Date date)

{

	return static_cast<int32_t>(date) / DAYS_IN_LEAP_YEAR;

}

/**

 * The date of the first day of the original base year.

 */

static constexpr TimerGameCalendar::Date DAYS_TILL_ORIGINAL_BASE_YEAR = DateAtStartOfYear(ORIGINAL_BASE_YEAR);

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

static constexpr TimerGameCalendar::Year MIN_YEAR = 0;

/** The default starting year */

static constexpr TimerGameCalendar::Year DEF_START_YEAR = 1950;

/** The default scoring end year */

static constexpr TimerGameCalendar::Year DEF_END_YEAR = ORIGINAL_END_YEAR - 1;

/**

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

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

 */

static constexpr TimerGameCalendar::Year MAX_YEAR = 5000000;

/** The date of the last day of the max year. */

static constexpr TimerGameCalendar::Date MAX_DATE = DateAtStartOfYear(MAX_YEAR + 1) - 1;

static constexpr TimerGameCalendar::Year INVALID_YEAR = -1; ///< Representation of an invalid year

static constexpr TimerGameCalendar::Date INVALID_DATE = -1; ///< Representation of an invalid date