Relatively speaking, you do know a birthdate, but, as you also know, the contemporary way of counting starts with Christ’s birth. Supposedly, as of this writing, it has been a few months over 2015 years since that event, that is, if you accept Dionysius Exiguus’ account. He might have been off by four to six years, so….
The Romans had a different “Year One,” and the Satanists in Rosemary’s Baby, the Soviets in 1917, and others had, at least temporarily, other “Year Ones.” So, at least something in your life is definitely, without question, undeniably, and certainly arbitrary (gotta love an oxymoron). The year of your birth, in the grand scheme of things past, is an arbitrary marker. We’ll accept it anyway for your sense of security.
“From the founding of the City” is a loose translation of the idiomatic Latin expression ab urbe condita. And we could just as easily use ab initio vobis, or roughly “from the beginning of you.” Let’s make the year of your birth “The Year One.” Got something definite sounding in that, don’t we?
Anything else arbitrary in your life? Any philosophical ideas you might suspect are just a bit contradictory around the edges. Some oxymorons hiding in your thoughts? Don’t fret. It happens to all of us. We find out that we can’t rely on much of the underlying foundations of our personal philosophies. And the same applies to our personal psychologies. We are, for the most part, calendars of conflicting dates: Someone is on the Julian calendar; someone else is on the Gregorian. Yet another is on the Mayan calendar (Wasn’t the world supposed to end a few years ago according to that calendar?).
Might that arbitrariness be a reason we have so much difficulty getting along? Someone elsewhere says, “This is my point of origin,” or “This is the anchor of my thought,” whereas someone else says, “No, this is the point of origin,” or “This is the anchor.” Starting points seem to make most, if not all, the difference.
Well, Happy Birthday, nevertheless. And if you don’t like the one you have, just start a new calendar.