Recertify on or before expiration date?

Hi,

my VCP-DCV expires on the 21st of Jan 2019 according to the VMWare certification manager. I plan to attempt re-certification at least a week before so I can fit in a second attempt should I fail.

My question is, if needed, can I book an exam for the 21st of Jan or do I need to attempt and pass by the 20th, i.e. before the 21st of Jan which is the date my VCP expiration?

Any links to confirm the answer either way would be appreciated.

Thanks