When loading data with LSMW, you can be stuck by incorrect date formating : Here is how to convert a field read in the file in DDMY (no matter what date separator the loading file provide) to SAP Date format YYYYMMDD : Add the following in the Mapping & Conversion Rules :

MATMAS9-ZKDAT+0(2) = MATMAS09-ZKDAT+6.
MATMAS9-ZKDAT+2(2) = MATMAS09-ZKDA+4.
MATMAS9-ZKDAT+4(4) = MATMAS09-ZKDAT.