Beside this, it seems a little odd, that Sam doesn't know Quincy's birthdate, as he knew it in "Scream to the Skies".
Possible goof: In this episode, Sam remarks that Quincy's birthday might be soon. Quincy corrects him as he says, that he had his birthday already. Requiring that episodes take place at least around the date they air, it is intended his birthday is in early December or in November, as this episode aired on December 8th. However, Quincy's birthday is celebrated in season 6s "Scream to the Skies", which aired on February 11th. However, we know that episodes of the show at least not always take place around the date they air, as season 7s "To Clear the Air" takes place in the summer, although it aired in February, so this might not be a goof at all.