Excel 2013 implements new spreadsheet functions, most for ODF / OpenFormula compatibility. See http://office.microsoft.com/en-us/excel-help/new-functions-in-excel-2013-HA103980604.aspx Calc already knows most of them and "just" needs to import/export the known functions.
Working on this.
Eike Rathke committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=24bce470788aa34e5e1bb001250bfa14cee1c75e import/export new Excel 2013 ODF functions, fdo#60032 The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Created attachment 73967 [details] testcase document The following functions are handled, name specialities are given as (in parentheses the en-US UI name) [in brackets the ODFF name] ACOT ACOTH ARABIC BASE BINOM.DIST.RANGE (B) [BINOM.DIST.RANGE] BITAND BITLSHIFT BITOR BITRSHIFT BITXOR COMBINA COT COTH CSC CSCH DAYS DECIMAL FORMULATEXT (FORMULA) [FORMULA] GAMMA GAUSS IFNA IMCOSH IMCOT IMCSC IMCSCH IMSEC IMSECH IMSINH IMTAN ISFORMULA MUNIT PDURATION (DURATION) [PDURATION] PERMUTATIONA PHI RRI SEC SECH SHEET SHEETS UNICHAR UNICODE XOR Notes: UNICHAR(0) differs in that it does not generate an error in LibreOffice.
With implementation of bug 57180 also NUMBERVALUE is imported/exported.
With implementation of bug 60322 also SKEW.P (SKEWP) [SKEWP] is imported/exported.