I am not sure if this method would take two InfoObjects.
Below note might help you .
http://service.sap.com/sap/support/notes/2024513
Instead of the Class/Method I tried a custom ABAP to interchange DATEFROM and DATETO . Can you try to comment the class/method portion and use this custom code ?
Here is the code :
DATA TEMP_DATE TYPE SY-DATUM.
LOOP AT SOURCE_PACKAGE_3 ASSIGNING <SOURCE_FIELDS_3> .
IF <SOURCE_FIELDS_3>-DATEFROM GT <SOURCE_FIELDS_3>-DATETO .
TEMP_DATE = <SOURCE_FIELDS_3>-DATETO .
<SOURCE_FIELDS_3>-DATETO = <SOURCE_FIELDS_3>-DATEFROM .
<SOURCE_FIELDS_3>-DATEFROM = TEMP_DATE .
CLEAR TEMP_DATE .
ENDIF .
ENDLOOP.
Regards
Anindya