ios NSDateComponents 时间计算方法

// 计算当前相隔多少天以后的日期NSDateComponents *comps = [[NSDateComponentsalloc] init];[comps setDay:1];NSCalendar *calender = [[NSCalendaralloc] initWithCalendarIdentifier:NSGregorianCalendar];NSDate *mDate = [calenderdateByAddingComponents:comps toDate:curdate options:1];//计算当前月有多少天NSInteger curMonthNumber = [[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:[NSDate date]].length;//根据两个时间点，定义NSDateComponents对象，从而获取这两个时间点的时差NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];NSDateComponents *dateComponents = [calender components:NSDayCalendarUnit fromDate:[NSDate date] toDate:mDate options:0];NSInteger  *resultDay =   dateComponents.day;