Date fields have useful variations which I would recommend before you throw the baby out with the bathwater. Perhaps you can use one of the other variations instead of unlinking the field.
{Date} is problematic as it shows today's date whenever it is updated


{CreateDate} is the date that the document was created (or the date you used SaveAs)
{SaveDate} is the date the document was last saved. This won't have a value until the doc has been saved at least once and the field is updated.

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Andrew Lockton
Chrysalis Design, Melbourne Australia