private List <int?> GetNextEditionStartDateDifferences(EditionEntity edition) { var nextEdition = _editionServices.GetNextEdition(edition, Utility.Constants.ValidEventTypesForCed); if (nextEdition == null) { return new List <int?> { null, null } } ; var weekDiff = edition.StartDate.GetValueOrDefault().WeekOfYearDiff(nextEdition.StartDate.GetValueOrDefault()); var dayDiff = edition.StartDate.GetValueOrDefault().DayOfYearDiff(nextEdition.StartDate.GetValueOrDefault()); return(new List <int?> { weekDiff, dayDiff }); }