Sorting datefolders and items does not work in v. 2.1.1. The sort order is set, but the items are never saved:

static void DoOrder(IEnumerable<IContent> contents)
{
    var sortOrder = 0;
    foreach (var objChild in contents)
    {
        objChild.SortOrder = sortOrder;
        sortOrder++;
    }
}

I solved it by just doing this instead:

static void DoOrder(IEnumerable<IContent> contents)
{
    ApplicationContext.Current.Services.ContentService.Sort(contents);
}