What makes an album 'a classic'

Having discussion with my daughter - half jokingly, but still, a discussion.

Albums come up and she says 'Thats a classic' and I say 'no.'.

What makes it a classic, as an example:

Red Hot Chili Peppers - To her, she says 'Californication' is a classic, but I say 'no' and say Mothers Milk or Blood Sugar Sex Magik is.

Does it matter on the age? Is she right? Am I? Neither of us?

 

I think Classic is a subjective/personal concept, I don't know if there's a cut off for how old it has to be

 

I started googling things, and sure, its subjective, I know....

But I guess a classic to one person may not be a classic to me... I suppose with enough hits on it, and an album you never get sick of hearing from start to finish, well, classified.