Format dates by using field codes
You can also use a formatting switch to get dates from a Date column in your spreadsheet to look exactly the way you want in your merged documents. If you insert a Date field into the main document and then press ALT+F9, you see this:
{ MERGEFIELD "Date" }
To get all the dates in the merged documents to have the format February 18, 2008 (regardless of how the dates are formatted in the worksheet cells), you can add this formatting switch to the field code:
{ MERGEFIELD "Date" \@ "MMMM d, yyyy" }