Although informal, this meaning is very common and is used in formal speech as well as writing. The meaning of the word dating shifted after the sexual revolution to include a more informal use referring to a romantic, sexual relationship itself beyond an introductory or trial stage, but prior to marriage. It falls into the category of courtship, consisting of social events carried out by the couple either alone or with others.
Dating is a stage of romantic relationships in which two individuals engage in an activity together, most often with the intention of evaluating each other's suitability as a partner in a future intimate relationship.