Unfortunately, not much, if anything at all, because cities during the Tang enforced a curfew. Tang Chang'an was a planned city built in accordance with Chinese geomancy principles. The city was square in shape and divided into wards, with each ward being an individual unit with its own gates and ward government. In just about every single Tang city, including the two capitals of Chang'an and Luoyang, a curfew was strictly enforced at night. The two main markets would shut down and all the ward gates were closed. Residents could not leave their ward after dark and even moving within the ward was regulated. See Chye Kiang Heng's Cities of Aristocrats and Bureaucrats, page 205.

It was the Song dynasty that finally abolished the curfew in its capital city of Kaifeng in 1063 and the markets were allowed to open twenty-four hours a day. If you're a hot-blooded young Han Chinese man looking for vice and wanton pleasures at night, you'd have much more fun in Song Kaifeng than you would in Tang Chang'an.