Adobe Pro error message will not accept 2 digit month and 4 digit year and send doc for signature

I have a document that I need to send for a signature. In the document there is a date range with just the 2 digit month and 4 digit year to another 2 digit month and 4 digit year. Adobe keeps giving me an error message. I change the format to custom and put it in the box just like on the document and it still will not let me send the document. I have a paid version of Adobe pro.