Oyungerel was one of my anthropology students (one of the best) when I taught at the National University of Mongolia in 2000-2001. This is from the celebration called Honhny bayar, roughly, the celebration of the bells. It was actually usually explained to me in English as "Last bells," although that's not a direct translation. It's sort of a graduation day, but in the process, the graduating class passes on the bell - which Oyungerel is holding - to the class which is about to become the seniors.
The actual ceremony lasted most of the day. My notes say it started around 10 or 11, and I left in the evening, and there were still events planned. It's graduation, but much more than that. The other students in the department do things for the seniors (and professors), there's much food and some drinks. The head of the department gave a five-minute "final lecture." There are various other things that go on, and then the students in all their finery pile into buses, and drive around town having pictures taken at numerous landmarks. Bottles are passed around on the bus. There's a lunch. Later the students go to a nightclub, and then to a retreat in Terelj for the weekend. (I opted out of the nightclub and weekend.)