//Create dictionary with attributes I care about and a fileList array

        NSMutableArray *fileList  = [[NSMutableArray alloc] initWithCapacity:10];
        NSDictionary *fileData = [NSDictionary dictionaryWithObjectsAndKeys:file, @"file", dateString, @"date", nil];

        [fileList addObject:fileData];

//I don't know how to sort this array by the "date" key!

        NSArray         *files = [fm contentsOfDirectoryAtPath:folderPath error:NULL];
    //iterate through files array
        for (NSString *file in files) {
            NSString *path = [folderPath stringByAppendingPathComponent:file];
    //code to create custom object with contents of file as properties
    //feed object to fileList, which displays it in the tableview

NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
[sortedFiles sortUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]];

NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
[sortedFiles sortUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]];