Created attachment 73147 [details] xlsx file that will be wrongly imported In the attached .xlsx file a cell has the **string** "DEC01". This is wrongly interpreted by libreoffice as a date rather than a text. It works correctly instead opening the equivalent.xls file. Operating System: Ubuntu Version: 3.6.2.2 release
Created attachment 73148 [details] An equivalent working .xls file
Created attachment 73149 [details] an other real-case example of wriongly xlsx file
Fixed in 3.6.4 with the fix for bug 55875 *** This bug has been marked as a duplicate of bug 55875 ***