iOS通过日期求星期 (蔡勒公式)

传人数据 20160128

- (NSString*)fromDateToWeek:(NSString*)selectDate

{

NSInteger yearInt = [selectDate substringWithRange:NSMakeRange(0, 4)].integerValue;

NSInteger monthInt = [selectDate substringWithRange:NSMakeRange(4, 2)].integerValue;

NSInteger dayInt = [selectDate substringWithRange:NSMakeRange(6, 2)].integerValue;

int c = 20;//世纪

int y = (int)yearInt%100;//年

int d = (int)dayInt;

int m = (int)monthInt;

if (m==1 || m==2)

{

m=m+12;

y=y-1;

}

int w =y+(y/4)+(c/4)-2*c+(26*(m+1)/10)+d-1;

    while(w<0){w+=7;}

    w%=7;

NSString *weekDay = @"";

switch (w) {

case 0:

weekDay = @"星期日";

break;

case 1:

weekDay = @"星期一";

break;

case 2:

weekDay = @"星期二";

break;

case 3:

weekDay = @"星期三";

break;

case 4:

weekDay = @"星期四";

break;

case 5:

weekDay = @"星期五";

break;

case 6:

weekDay = @"星期六";

break;

default:

break;

}

return weekDay;

}