The opera mask on the forecourt is the only giveaway, save for the Chinese sign, that this modern block is actually an opera house. Chang'an Grand is more a place for connoisseurs than tour groups, with seating for 800 and its own teahouse. Usually has English captions.
Matinees, when it has them, start at 2pm; evening performances start at 7.30pm. Most shows last for around two hours. Buy tickets in person from the ticket office here, or ask your hotel to help you buy them on WeChat. Shows rarely sell out, but the cheaper seats often do.