I have to attend a feast for a daily quest, I have entered several, but it doesn’t say the quest..

Feast typically lasts 12-24 hours unless the guests fill the seats. If by any chance, you are just trying to attend ones from whom you do not know, or not planned by your guild/alliance, there is a chance that these feasts won't be occupied at their seat limit -- which means you will have to wait until the event finishes or triggered manually by the host to end it earlier than the actual remaining duration.