"Be the order of the day" essentially means a particular trend or behavior that is prevalent in a particular context. Here are some synonyms that can be used in place of this phrase. 1. Prevailing: Refers to something that is dominant or widespread in a given environment. 2. In vogue: A term used to describe something that is currently popular or fashionable. 3. Customary: This word refers to a behavior or manner that is traditionally followed in a particular society or group. 4. Standard: Describes an established norm or expectation within a particular context 5. Typical: A synonym for "be the order of the day" that refers to a behavior or trend that is common or expected in a specific context.