获取前一天日期（应对跨月取日期问题）

获取今天的日期

-(NSString *)getDate{

    NSDateFormatter*formatter = [[NSDateFormatteralloc]init];

    [formatter setDateFormat:@"YYMMdd"];

    NSString *locationString=[formatter stringFromDate: [NSDate date]];

    [formatter release];

    return locationString;

}

获取前一天日期

-(NSString *)getPredate:(NSString *)strDate

{

    NSDateFormatter*formatter = [[NSDateFormatteralloc]init];

    [formatter setDateFormat:@"YYMMdd"];//MAC10.8的系统注意“YY”要小写，否则会减一年，iOS暂时不区分

    NSDate *locationdate=[formatter dateFromString:strDate];

    NSDate *predate = [NSDatedateWithTimeInterval:-24*60*60 sinceDate:locationdate];

    NSString *locationString = [formatter stringFromDate:predate];

    [formatter release];

    return locationString;

}