iOS如何将日期字符串转成NSDate

没事玩新浪微博， 可取得日期字符串"Wed May 2 22:27:08 +0800 2012", 想做日期计算，想转成NSDate，根据网上资料，可先设置对应的NSDateFormatter,然后再从其转成对应的NSDate, 对应的代码片段如下：

NSString* dateStr = @"Wed May 2 22:27:08 +0800 2012";

    NSDateFormatter* formater = [[NSDateFormatter alloc] init];

    [formater setDateFormat:@"EEE MMM d HH:mm:ss zzzz yyyy"];
    NSDate* date = [formater dateFromString:dateStr];
    NSLog(@"%@", date);
   
    //NSDate* now = [NSDate now];
    double inter = fabs([date timeIntervalSinceNow]);
    if( inter < 60)
        NSLog(@"1 mins ago!");
    else if(inter < 60*60)
        NSLog(@"1 hours ago!");
    else if(inter < 60*60*24)
        NSLog(@"1 days ago!");
   
    NSLog(@"interval is %f min", inter/60);