Birthdays are strange buggers. They're part of our identity almost from the time we're born. The determine when we start school, when we are eligible to learn to drive, when we're old enough to marry, join the army and vote.
And then... well, then there are no more milestones to mark until we retire and start drawing Social Security. So it's small wonder that after a while we stop "celebrating" that turn over to another year. Women seem to do this more than men on a conscious basis. Men ignore the entire concept, mostly.
Actually my sons always seemed to be confused by the idea of celebrating their birthday. I remember one year my oldest son was about seven. With furrowed brow he demanded, "You mean I get presents just for being born?"
His brother at six was more pragmatic. He belted my older son on the shoulder and told him to be quiet. If someone wanted to give them presents, well why not? Presents are a good thing.
So I just want to mention that today is my friend's birthday. Oh, she doesn't celebrate it... so we won't tell anyone, right? But it never hurts to offer blessings and good wishes. Happy Birthday, Jane.