أَتَى زَيْدٌ بَعْدَ الْمَغْرِبِ
Zayd came after sunset.
- بَعْدَ is mudaf; الْمَغْرِبِ is mudaf ilayh.
- Here the phrase answers when did Zayd come?
- Therefore بَعْدَ الْمَغْرِبِ is an adverbial expression of time in this sentence.
A familiar adverb does not receive its role from its dictionary meaning alone. The sentence meaning remains decisive.