比较两个日期的方法

-(int)compareOneDay:(NSString *)oneDay withAnotherDay:(NSString *)anotherDay

{

    NSDateFormatter* dateFormat = [[NSDateFormatter alloc] init];//实例化一个NSDateFormatter对象

    [dateFormat setDateFormat:@"yyyy-MM-dd HH:mm"];//设定时间格式,要注意跟下面的dateString匹配

    NSDate *date1 =[dateFormat dateFromString:oneDay];

    NSDate *date2 =[dateFormat dateFromString:anotherDay];

    

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm"];

    NSString *oneDayStr = [dateFormatter stringFromDate:date1];

    NSString *anotherDayStr = [dateFormatter stringFromDate:date2];

    NSDate *dateA = [dateFormatter dateFromString:oneDayStr];

    NSDate *dateB = [dateFormatter dateFromString:anotherDayStr];

    NSComparisonResult result = [dateA compare:dateB];

    NSLog(@"date1 : %@, date2 : %@", oneDay, anotherDay);

    if (result == NSOrderedDescending) {

        return 1;//大于

    }else if (result == NSOrderedAscending){

        return -1;//小于

    }

    return 0;//相等

}