1、首先获取当前日期NSDate形式，指定一个日期格式

#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;  
}  

2、然后将指定日期（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"];  

3、最后进行比较，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;  
      
}  

调用

[self compareOneDay:[self getCurrentTime] withAnotherDay:date]