The idea of this is something that I can't get interested in. A birthday is a birthday, whatever the age. When my husband asked me if I wanted to celebrate a so-called 'big birthday' I pointed out that the day before I was one day below the number, and the next day I was one day above it.
I was lucky enough to celebrate my 50th in Vegas, when my twin turned fifty eight hours before me, even though I was 10 minutes older than her.
I just can't understand why a birthday that ends in a 0 as you get older is something special.