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]