//
//   Usage: rd = rd_from_gregorian( GDATE *gdate )
//   Description: Compute the R.D. date (rd) given a gregorian date (GDATE *gdate).
//
int
rd_from_gregorian(GDATE *gdate)
{
        GDATE rd;
        rd = gregorian_epoch - 1 + 365 * (gdate.year - 1) + floor((gdate.year-1)/4) - floor((gdate.year - 1)/100) + floor((gdate.year-1)/400) + floor((367*gdate.month-362)/12);
    if (gdate.month <= 2) {
         rd = rd + 0;
    } else if ((gdate.month > 2) && (gregorian_leap_year(gdate.year) == 1)) {
         rd = rd - 1;
    } else {
         rd = rd - 2;
    }
    rd = rd + gdate.day;
    return rd;
}

//
//   Usage: gregorian_from_rd( int rd, GDATE *date )
//   Description: Compute the gregorian date (GDATE *date) given a  R.D. date (rd).
//
void
gregorian_from_rd(int rd, GDATE *gdate)
{
    gdate.year = gregorian_year_from_rd(rd);

    GDATE prior_days = rd - rd_from_gregorian(january, 1, gdate.year);
    int correction = 0;
    if (rd < rd_from_gregorian(march, 1, gdate.year)){
        correction = 0;
    }else if (rd >= rd_from_gregorian(march, 1, gdate.year)&&gregorian_leap_year(gdate.year)){
        correction = 1;
    }else{
        correction = 2;
    }
   gdate.month = (12*(prior_days + correction)+373)/367;
   gdate.day =rd - rd_from_gregorian(gdate.month, 1, gdate.year)+1;

   return gdate.month, gdate.day, gdate.year;

}


static int
paschal_moon( int g_year )
{
        GDATE rd;
        int century = (g_year/100)+1;
        int shifted_epact = (14 + 11* (g_year % 19) - ((3*century)/4)+((5+8*century)/4))%30;
        int adjusted_epact;
        if (shifted_epact == 0 || shifted_epact == 1 && g_year % 19 > 10){
                adjusted_epact = shifted_epact + 1;
        }else {
                adjusted_epact = shifted_epact;
        }
        rd = rd_from_gregroian(april, 19, g_year) - adjusted_epact;
        return rd;
}


//
//   Usage: rd = labor_day( g_year )
//   Description: For any gregorian year (g_year), determine the R.D. date of Labour Day.
//   Labour Day is the first Monday in September, on the gregorian calendar.
//
int
labor_day( int g_year )
{
        return kday_on_or_before(rd_from_gregorian(September, 1, g_year), 1 );
}

//
//   Usage: rd = christmas( g_year )
//   Description: For any gregorian year (g_year), determine the R.D. date of Christmas.
//   Christmas falls on December 25, on the gregorian calendar.
//
int
christmas( int g_year )
{
    GDATE date;
    date = (December, 25, g_year);
    return rd_from_gregorian(date);

}

//
//   Usage: rd = daylight_savings_start( g_year )
//   Description: For any gregorian year (g_year), determine the R.D. date for the start of Daylight Savings Time.
//   Daylight Savings Time starts on the first Sunday of April, on the gregorian calendar.
//
int
daylight_savings_start( int g_year )
{
    GDATE date = kday_on_or_before(rd_from_gregorian(April, 1, g_year), Sunday);
    return rd_from_gregorian(date);

}


//
//   Usage: rd = daylight_savings_end( g_year )
//   Description: For any gregorian year (g_year), determine the R.D. date for the end of Daylight Savings Time.
//   Daylight Savings Time ends on the last Sunday of October, on the gregorian calendar.
//
int
daylight_savings_end( int g_year )
{
    GDATE date = kday_on_or_before(rd_from_gregorian(October, 1, g_year), Sunday);
    return rd_from_gregorian(date);

}