As old as the hills
Definition 1 of 1
Pro Tip 1/3Hyperbolic idiom
Used to exaggerate age, showing something is extremely old or outdated. 
That type of phone is as old as the hills; you rarely see them anymore.
Pro Tip 2/3Humorous undertone
Often used humorously to describe something amusingly out of date. 
Grandpa's jokes are as old as the hills, but they still make us laugh.
Pro Tip 3/3Not literal
Doesn't mean literally as old as hills; it's a figurative speech to stress oldness. 
This textbook is as old as the hills, it's time for a new edition.