The issue is not with the date switch. I've used them extensively will all manner of dates, with no such '12' problem. See, for example, my
Microsoft Word Catalogue/Directory Mailmerge Tutorial, in the 'Sticky' thread at the top of this forum:
Microsoft Word Catalogue/Directory Mailmerge Tutorial
What short date format does your system's regional date setting use, and what date format does your Excel workbook use?