The Data Formatting disclosure in the Inspector has that functionality.
In layout mode, select the merge field (or the string of text that contains the merge field) and then in the inspector, go to the Data tab and down at the bottom is the section for Data Formatting. In there, you will see a few buttons, one of which is for Date and the other for Time. Select the Date button and then you can set your desired formatting. Select the Time button and set your formatting.
Nick, thanks for your pointer. I have the VisitDate set as entered e.g. 1/9/2013. But I want the merge field <<VisitDate>> to be in the format of Wednesday, January, 9th, 2013.
Doug, Thanks for your reply. For a merge field <<VisitDate>>, how to get to the inspector? I can double-click to go to the inspector for a normal field. But everything is treated as text in a letter for the merge field <<VisitDate>>.
Single-click (select) the merge field text-box. You can open the Inspector (and keep it open) either using the Inspector button or by typing Command-I.
I tried the inspector button and Command-I and it worked.
Thank you so much!