To clarify, I've asked the question on ELL, and received unsatisfactory results, and this site seems to be my last hope.
In an English textbook used in China, a sentence reads like this:
We (Chinese) eat boat cakes at the Dragon Boat Festival.
I think the preposition AT is wrong, and ON should be the right one to use in this sentence because: there IS a set date for the Dragon Boat Festival, which lasts for one day, and there are almost NO activities held at home NOR events for anybody to go to, except that some Chinese eat the "boat cakes" (at home). The festival in question commemorates an ancient patriotic poem in Chinese history, but in reality, modern Chinese baically take it as a very good excuse to have a day off, and hence it became a 1-day national holiday as of 2008.
Am I right to use ON?
Please feel free to believe or confirm that "the Dragon Boat Festival in itself is a problematic term or translation", and hence the sentence is invalid and has to be rephrased.