Get past performances within a date range

Hello all,

I am building a calendar of performances and need to get all past performances from this month.  I am trying to use the web API function of GetPerformancesEx4 but it only seems to return future performances.  Below is my code.  Perhaps I am calling the function incorrectly or just using the wrong function all together for my needs.  Thanks for any help you can provide!

                string sessionKey =
                    HttpContext.Current.Session[TessSessionKeySessionKey].ToString();
                short modeOfSale = (short)HttpContext.Current.Session[ModeOfSaleSessionKey];
                DataSet results = unsecuredClient.GetPerformancesEx4(
                    sWebSessionId: sessionKey,
                    sStartDate: Convert.ToDateTime("06-01-2013").ToString("yyyy-MM-ddTHH:mm:ss"),
                    sEndDate: Datetime.Now.ToString("yyyy-MM-ddTHH:mm:ss"),
                    iVenueID: (short)-1,
                    iModeOfSale: modeOfSale,
                    iBusinessUnit: defaultBusinessUnit,
                    sSortString: "",
                    sKeywords: "",
                    cKeywordAndOrStatement: "",
                    sArtistLastName: "",
                    sFullText: "",
                    sFullTextType: "",
                    sContentType: "",
                    sPerformanceIds: "",
                    sSeasonIds: "",
                    bIncludeSeatCounts: false);