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 = [[NSDateComponents alloc] init];

//    [comps setDay:[NSDateUtils getDay:date]];

//    [comps setMonth:[NSDateUtils getMonth:date]];

//    [comps setYear:[NSDateUtils getYear:date]];

//    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

//    NSDate *endDate = [[NSDate alloc] init];

//    NSDate *startDate = [gregorian dateFromComponents:comps];

//    [comps release];

//    unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;

//    NSDateComponents *comps2 = [gregorian components:unitFlags fromDate:startDate toDate:endDate options:0];

//    [gregorian release];

//    [endDate release];

//    int days = [comps2 day];
   
NSDateFormatter *dateFormatter = [[[NSDateFormatter
alloc] init]
autorelease];
    [dateFormatter
setDateFormat:@"yyyy-MM-dd"];

    [dateFormatter setCalendar: [NSCalendar
autoupdatingCurrentCalendar]];
   
NSDate *today = [dateFormatter
dateFromString:[dateFormatter stringFromDate:[NSDate
date]]];
   
NSDate *startDate = [dateFormatter
dateFromString:[NSDateUtils
getyyyyMMddDate:date]];
   
NSDate *formatterStartDate = [dateFormatter
dateFromString:[dateFormatter stringFromDate:startDate]];
   
NSTimeInterval interval = [today
timeIntervalSinceDate:formatterStartDate];
   
NSInteger days = ((NSInteger)interval)/(3600*24);
   
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:(longlong)date {

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

    NSDateComponents *comps = [[selfshareNSCalendar]components:unit
b7a4
Flags
fromDate:[NSDatedateWithTimeIntervalSince1970:date]];
   return comps;
}