Date fields can be added either to customise your document when sending, or for signers to complete, or which are filled out automatically when the signer visits the document. They can be added as sender or signer fields to your PDF on the PDF Edit page.
Signer dates fields can be dragged and dropped onto a document from the left-hand side of the edit page. The format is set to "dd/mm/yyyy (auto sign date)". "Auto sign day" is the key bit here. It means the signing date will go in automatically when the signer accesses their document. To change the format click on the field and on the field type/validation dropdown and select the date format required.
The format is set as dd/mm/yyyy. To change the format click on the field to see its form and then click the 'Type/Validation' option and select another format, e.g. mm-dd-yy.
Scroll down the list of field type/validation options to see all the many possible date formats available