计算某个日期与当前日期相隔的天数

//返回0
当天，1昨天，2前天，以此类推

//之前那样用时间差来整除一天的秒数，计算出来的天数有误差

+ (int)getDaysFromAnotherDay:(longlong)date {//date是时间戳

//    return [self getDaysFrom1970:date] - [self getDaysFrom1970:[[NSDate date] timeIntervalSince1970]];

NSDateComponents *comps = [[NSDateComponentsalloc]
init];

[compssetDay:[NSDateUtilsgetDay:date]];

[compssetMonth:[NSDateUtilsgetMonth:date]];

[compssetYear:[NSDateUtilsgetYear:date]];

NSCalendar *gregorian = [[NSCalendaralloc]
initWithCalendarIdentifier:NSGregorianCalendar];

NSDate *endDate = [[NSDatealloc]
init];

NSDate *startDate = [gregorian
dateFromComponents:comps];

[compsrelease];

unsignedint unitFlags =NSYearCalendarUnit |
NSMonthCalendarUnit |NSDayCalendarUnit;

NSDateComponents *comps2 = [gregorian
components:unitFlags
fromDate:startDatetoDate:endDate
options:0];

int days = [comps2
day];

return days;

}

+ (int)getYear:(longlong)date {

return [[selfgetNSDateComponents:date]
year];

}

+ (int)getMonth:(longlong)date {

return [[selfgetNSDateComponents:date]
month];

}

+ (int)getDay:(longlong)date {

return [[selfgetNSDateComponents:date]
day];

}

+ (NSDateComponents *)getNSDateComponents:(long
long)date {

NSInteger unitFlags =
NSYearCalendarUnit | NSMonthCalendarUnit |
NSDayCalendarUnit | NSWeekdayCalendarUnit |
NSHourCalendarUnit | NSMinuteCalendarUnit |
NSSecondCalendarUnit;

NSDateComponents *comps = [[self
shareNSCalendar]
components:unitFlags fromDate:[NSDate
dateWithTimeIntervalSince1970:date]];

return comps;

}