As a follow-up to missinglinq comments; what is meant by "backdating". For example, if the entry has to be the current date and no other, then you can lock the date field as use the DATE function to set the date (default value).
If there is a degree of latitude, you can use DateDiff for testing. In my case, when I receive a project I may not immediately enter it. So I have a test that asks for filing date verification should the received date be greater than seven days prior to the current date.