You can add a linked Date Picker Content Control to your document and edit the properties to show the desired format. Then duplicate that Content Control and alter the properties to show the date and time in a different format. You will be able to change any one instance and have all the others show their regionalised version of the same.

The easiest way to get the first linked date picker is to go to Insert > Quick Parts > Document Property > Publish Date. You then edit the properties by selecting it and going to the Developer Tab and clicking the Properties button.

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Andrew Lockton
Chrysalis Design, Melbourne Australia