When updating a waitlist status, if you accidentally forget to change the status date, the only way to correctly change the date of the status is to change the status again to something else, then change it back with the correct date.

For example, if you were wanting to change the status from "Referred" to "Active", if you set it to "Active" and hit save, then went oops! and updated the date, that status date will remain the same and it will ignore the new date you set.

You would have to set the status back to "Referred" again (or any other status), then make sure you've entered the correct date and choose the status "Active" for a second time.

It looks like there is no record update for the Waiting List Status History unless the status itself changes. It only adds new records, and does not update existing ones.