Indentation on a long (ish) linq chain

I have some code that loops through directories named for years (e.g. /2011/, /2012/ etc) which each contain files whose names end with dates in the "yyyyMMdd" format, and builds a list of all the dates in all the directories. But what is the best way to indent this, nothing I've tried is readable:

files = files.Union(
    Directory.GetFiles(year)
             .Select(d => DateTime.ParseExact(
      Path.GetFileNameWithoutExtension(d)
          .Substring(
         Path.GetFileNameWithoutExtension(d)
             .Length - 8),
     "yyyyMMdd",
     null))).ToList();

or

files = files.Union(Directory.GetFiles(year)
                             .Select(d => DateTime.ParseExact(
                                                              Path.GetFileNameWithoutExtension(d).Substring(
                                                                                                    Path.GetFileNameWithoutExtension(d).Length - 8),
                                                              "yyyyMMdd",
                                                              null)
                                     )
                    ).ToList();

or

files = files.Union(Directory.GetFiles(year)
                             .Select(d => DateTime.ParseExact(
                                                              Path.GetFileNameWithoutExtension(d).Substring(
                                                                                                            Path.GetFileNameWithoutExtension(d).Length - 8),
                                                              "yyyyMMdd",
                                                              null))).ToList();

or

files = files.Union(Directory.GetFiles(year).Select(d => DateTime.ParseExact(
                    Path.GetFileNameWithoutExtension(d).Substring(
                    Path.GetFileNameWithoutExtension(d).Length - 8),
                    "yyyyMMdd", null))).ToList();

I would consider refactoring the .Select call to do this:

files = files.Union(Directory.GetFiles(year).Select(d => GetTimeForFile(d))).ToList();

Where GetTimeForFile is a method with the following content:

DateTime GetTimeForFile(String fileName)
{
    var noExtName = Path.GetFileNameWithoutExtension(fileName);
    return DateTime.ParseExact(noExtName.Substring(noExtName.Length - 8),
     "yyyyMMdd", null);
}

Either way, no matter how you indent it now, the method extraction of GetTimeForFile makes it significantly more readable.

StackExchange Code Review Q#64358, answer score: 10