thing of the past

thing of the past (plural things of the past)

1. (idiomatic) Something that has gone extinct or become obsolete.
   • 2010, Jo Nesbø, translated by Don Bartlett, “The Snowman”, in The Snowman (Harry Hole; 7), London: Harvill Secker, →ISBN, part 5, page 403:

     ‘And in fact I found something interesting in the sample of the boy you were talking about. The son of Hole’s girlfriend.’ / ‘My understanding is that their relationship is now a thing of the past.’

It occurs most commonly with become, sometimes with be, and occasionally with seem.

• go the way of the dinosaurs
• go the way of the dodo