The wedding ceremony will still be basically the same, even down to a lot of the details. There'll be cake, a special dress only worn by the bride once, rice being thrown at the couple as well as groomsmen and bridesmaids.
Christmas will still be around, same as New Year's. Single people will still get bummed out every 14th of February.
Major religions will keep on trucking, as will the successor forms of many national governments. The law courts will also maintain continuity of a type.
Some of the companies that are around today may even still be going, albeit in a highly modified form.