There's no such thing IMHO.
Names that people on MN are always calling classic and timeless are always soooo of their time.
DH had a mate at school with a really odd and unusual name that he got a lot of teasing for - it was Thomas. Yes really! Because everyone else then was called Steve and Dave and Paul and Mark.
I think maybe Elizabeth fits the bill as I can think of people of all ages I know called it; and maybe Kate/Katherine. There aren't many tho. Why worry? All the Julies and Karens that I know seem to be OK even tho everyone knows from the name exactly how old they are
(in their early 40s btw)
Looking at names people have posted here - Grace for instance, a lovely name, but not one that many people were called 40 years ago. I have never met a Grace born longer ago than the early 90s.
sugarandspice I love your list and it includes my DD's name! Her name is one of the less common ones you list (well I don't know any others) but a lot of them are in the mould of names that are coming back - Florence, never met any as a child, ditto Harriet, but popular 100 years ago. NAmes go in cycles, why fight it? Pick one you liek and hopefully you will still like it in years to come. I still love myDCs' names and the oldest is nearly 13 