What's my age again?
Besides my memory and social artifacts, what evidence do I have for my age? If I wake up, there is nothing I can readily look at or think about that says, yes, there have been approximately 21 cycles of the Earth's orbit around the Sun since I first came to existence in this world. And when did I come to existence? Was that when I was first aware? Or how about when my first baby picture was taken? Whatever it is, I haven't been keepinng a tally about how many multiples of 365 days have elapsed since then.