Ling orderby and groupby

Question

I have the following code. And I want the group by groups (i.e. the years and months) to be sorted ascendingly. How can I do this? Thanks.

Code Snippet

                var AList = from an in db.Announcements
                            group an by an.EnteredOn.Year into YearGroups                         
                            select
                                new
                                {
                                    Year = YearGroups.Key,
                                    MonthGroups =
                                        from an2 in YearGroups
                                        group an2 by an2.EnteredOn.Month into MonthGroups
                                        select
                                            new
                                            {
                                                Month = MonthGroups.Key,
                                                Announcements = MonthGroups
                                            }
                                };