Using Sharpnote.net to connect to Simplenote and return notes from the index

gistfile1.cs

var email = "user@example.com";
var password = "password";
var repo = SharpnoteRepository<Note>.Instance;

if (repo.Connect(email, password))
{
    repo.GetIndex()
        .OrderBy(rn => rn.Modified)
        .ToList()
        .ForEach(rn => Console.WriteLine(rn.Modified.ToString()));                    
}

I get an exception when running this piece of code :

Cannot parse value: 1289316291.789368 as seconds for DateTimeOffset