1、首先獲取當前日期NSDate形式，指定一個日期格式

#pragma mark -得到當前時間  
- (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、然後將指定日期（此處以2016-09-30-00點為例）轉換為同樣日期格式，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、最後進行比較，將現在的時間與指定時間比較，如果沒達到指定日期，返回-1，剛好是這一時間，返回0，否則返回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;        
} 

4、比較

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