Literally “of/from yesterday”.
- (idiomatic, predicative) outdated
- DVDs sind von gestern. Du brauchst Blu-Ray.
- DVDs are antiquated. You need Blu-ray.
- (idiomatic, chiefly in negation, predicative) born yesterday
- Ich bin doch nicht von gestern!
- I wasn't born yesterday!
- The two senses are contradictory. Sense 1 is based on yesterday meaning “of the past” (and hence “obsolete”), whereas sense 2 is based on the same word meaning “recent” (and hence “unexperienced”). This may lead to some confusion, though rarely to actual misunderstandings.