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# Correction calendar notation

Video transcript

I told you in the last video
on calendar notation that, regardless of whether you're
using BC, AD or BCE and CE, that there is no year
0, that we had 1 BC. And then we had that
theoretical birth of Jesus, and most historians
don't think that he was born right exactly
on January 1, 1 AD. But there's no year 0. Right after that, you
go from December 31, 1 BC, to January 1, 1 AD. There's no year 0. And despite the fact
that I emphasized that in the last video, I didn't
take that into consideration when I calculated
how many years there were between Plato's birth
and Columbus discovering the new world. And the reason why I didn't
take that into consideration is that the year
1492, whether you want to call it AD
1492, Anno Domini 1492. Whether you want
to call it that, or whether you want to call
it 1492 in the Common Era. It's not 1492 years since the
theoretical birth of Jesus, which we know is not
the actual birth. He was probably
born before that. It is 1,491 years since
the birth of Jesus. And to think about
it this way, let's just assume-- I'll
keep emphasizing, it's a theoretical date
that we're talking-- or the theoretical event,
this kind of birth of Jesus that our calendars
revolve around. If we talk about January 1,
let's think about it this way. So January 1, 1
in the Common Era. How long is that since
the birth of Jesus? It's not one year. You wouldn't just
look at this and say it's been one year, because
this is theoretically the day that he was born. So this is zero years,
or almost zero years since that theoretical
birth of Jesus. Another way to think about it
is how long after January 1, the year 1 before
the Common Era-- and I could've
called this AD, and I could've called this
BC-- what's the time difference between
these two dates? So the way I calculated
it before, I said, oh, this is one year after
that theoretical birth. That's wrong. This is during that
theoretical birth. But if I did it the way
I did in the last video, I would have said, oh,
that's one year after, one year before. You add them together,
and you would get two. But that's wrong because
there is no year 0. So January 1, 1 AD, or 1 in the
Common Era is right over here. And then January 1, 1 BCE, is
exactly one year before that. So there's only one year,
one year difference. And the reason why
the math is strange is because there is no year 0. If there was a year 0, then my
calculation in the last video was correct. So really, the way that
you would calculate the time between Plato's birth
at 428 BC and Columbus sailing across the Atlantic in
1492, you would say, OK. This is 428 years before that
theoretical birth of Christ. But this isn't 1,492 years
after that theoretical birth. This is 1492 minus 1. So what you would do is you
would add these two numbers. This is 428 before. This is 1,492 minus
1 years after. So you would add them
and then subtract 1. So the correct answer-- so
this is the correction part-- it isn't 1,920 years between
Plato's birth and Columbus. We want to subtract 1 from that. It is 1,920 minus 1 years. So that is 1,919 years. The same way that the difference
between 1 AD and 1 BCE, you could almost view it as
positive and negative numbers. You say, oh, this is
positive 1 minus negative 1. That would give me two. But there is no 0, so you would
need to subtract another 1. So this is exactly
1 year difference. So just want to clarify that. That's what that no
year 0 does to us.