Date

-(int)compareDate:(NSString*)date01 withDate:(NSString*)date02{
    dateNum = 0;
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    [df setDateFormat:@"yyyy-MM-dd"];
    NSDate *dt1 = [[NSDate alloc] init];
    NSDate *dt2 = [[NSDate alloc] init];
    dt1 = [df dateFromString:date01];
    dt2 = [df dateFromString:date02];
    NSComparisonResult result = [dt1 compare:dt2];
    switch (result)
    {
            //date02比date01大
        case NSOrderedAscending: dateNum=1; break;
            //date02比date01小
        case NSOrderedDescending: dateNum=-1; break;
            //date02=date01
        case NSOrderedSame: dateNum=0; break;
        default:
//            NSLog(@"erorr dates %@, %@", dt2, dt1);
            break;
    }
    return dateNum;
}