You can’t wait for them when you are young and you dread them when you are old. There is however something perverse and self-consuming in the idea of yearly celebrations for like all habits they have a function both to cement our idea of ourselves and our acceptance of the community. But with birthdays comes the whole idea of growing older and thereby weaker, or marking a regular milestone and separately marking out significant millstones such as the beginning of new decades.
But actually it is entirely meaningless. In a universe that is eight billion years old, part of a planet that is four and a half billion years old, and part of a species that might have ancestry as far back as a million years with recorded history of thousands of years what could fifty or sixty or a hundred years actually mean? It isn’t as long as it takes to snap one’s fingers in terms of what goes on in the universe.
But birthdays are not about equivalency, they are there to confirm that a particular human being has ‘made-it’ and today no one even thinks about this very much they just accept that every year one must accept another year has gone. Celebrations always seem fairly arbitrary but amongst them, birthdays must be the least serious and most persistent.