5pm - the official opening of the New Bonn Square, with entertainment from the Illustrious Sambizas (Brazilian band), Les Grooms (French brass band weirdness), Christmas lights switch on and a word from Lady Suzanna, our Lord Mayor. As someone who walks past it daily, I can reveal three things -- it has super non-slip paving, enormous metal light towers, and a lovely little grove of trees.
6.20pm - Huge illuminated stilt walkers will start taunting the crowd, eventually (with the help of many Oxford schoolchildren) chivvying them into a long, lantern-lit procession* (6.30pm) up Queen Street, along Cornmarket and into Broad Street...
7pm - Broad Street goes pyrotechnical with the Walk the Plank fire and aerial sculpture show and The Big Bang's huge sausage BBQ. "Hot apple punch" is also promised, but I would also like point out several pubs in the vicinity (and maybe go on to one?)
More details (including details of late opening and projection shows at the musuems and modern art oxford, and the castle complex where there's a big earth from the air exhibition on at the moment) in this PDF here, or navigate to it yourself from Oxford Inspires.
*If following processions seems a bit too structured, you can stay in Bonn Square, or in Cornmarket, for Decibel, Messy Jam, Freefall, Flaw'r Artists, Sol Samba and all of the other usual suspects of Oxford street-parties, with refreshments/etc. being served out of the Baptist Church and St Michael's.