Weddings
Provided there's no funny rules and a grand entrance is being made, girls go for it and be late. The ceremony needs build up and drama. The more formal the event, the later you should be. Maybe you can go by train length.
No train/short train = 10 minutes Medium train = 20 minutes Long train = 30 minutes Huge train = as late as you want - no less than 45 minutes
My sister looked amazing in a gown that flowed the length of the church and was 58 minutes late.
There should be musical entertainment for guests while waiting and maybe a social atmosphere - not too stuffy - then a 5 minute bell and take your seats. It's all part of the event. Mine's at 11. I'm thinking of getting a pro musician to give a concert from 11 to 12.15 then a social with some of the key family there until 12.50 then ring the bell and I enter at 1pm. So, everyone gets great entertainment and I am officially 2 hours late! Then , social afterwards with me - and I don't want to be stuffy like some people.