When trading with some of the pigs, after a trade or three, they'll refuse to accept any more items, saying, "come'st back on the morrow," which seems to suggest that, once a new day starts, they will accept more trades. But many days passed, and the pigs would still not accept any trades, repeating, "come'st back on the morrow."
Steps to Reproduce
Trade with pigs until they refuse more trades, days pass and they still won't accept new trades
Trade with pigs until they refuse more trades, days pass and they still won't accept new trades