Most people end up not knowing how long the’ve lived, ever! They belittle the number of years (put simply “how long”) they’ve been on earth by a simple oversight: a birthday is not too mark the beginning of a new year of your life but to mark the end of a completed year.
A man born on 13 May, 1920 died on 4 September 1993. On his gravestone was written, “He lived 73 years”. What a lie. Yes, he celebrated his 73rd birthday but this dude sure lived more than that.
The very first birthday celebrated by a human is painful. It is you 0th birthday. The first gift given to you is a spank from the doctor while hiding you upside-down. And your vote of thanks is a loud cry. After that, you started your first year of life. You just marked the end of your zeroth year of life and started your first.