iOS比较当前日期与指定日期大小

    #pragma mark -得到当前时间
    - (NSDate *)getCurrentTime{
        NSDateFormatter *formatter=[[NSDateFormatter alloc]init];
        [formatter setDateFormat:@"dd-MM-yyyy-HHmmss"];
        NSString *dateTime=[formatter stringFromDate:[NSDate date]];
        NSDate *date = [formatter dateFromString:dateTime];  

        NSLog(@"---------- currentDate == %@",date);
        return date;
    }  

将指定日期（此处以2016-09-30-00点为例）转换为同样日期格式，返回NSDate形式

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd-MM-yyyy-HHmmss"];
NSDate *date = [dateFormatter dateFromString:@"30-09-2016-000000"];  

将现在的时间与指定时间比较，如果没达到指定日期，返回-1，刚好是这一时间，返回0，否则返回1

    - (int)compareOneDay:(NSDate *)oneDay withAnotherDay:(NSDate *)anotherDay
    {
        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"dd-MM-yyyy-HHmmss"];
        NSString *oneDayStr = [dateFormatter stringFromDate:oneDay];
        NSString *anotherDayStr = [dateFormatter stringFromDate:anotherDay];
        NSDate *dateA = [dateFormatter dateFromString:oneDayStr];
        NSDate *dateB = [dateFormatter dateFromString:anotherDayStr];
        NSComparisonResult result = [dateA compare:dateB];
        NSLog(@"date1 : %@, date2 : %@", oneDay, anotherDay);
        if (result == NSOrderedDescending) {
            //NSLog(@"Date1  is in the future");
            return 1;
        }
        else if (result == NSOrderedAscending){
            //NSLog(@"Date1 is in the past");
            return -1;
        }
        //NSLog(@"Both dates are the same");
        return 0;  

    }  

使用