When was Jesus actually born (year)? If he wasn’t born in what we consider the year 0, why do we remember this year specifically and not another one as the year 0?

Honestly, we don't know. More can always be said on the matter, so if anyone would like to have a go at this little snarl in the chronology, please don't let this post stop you! For the meantime, OP, you may be interested in u/J-Force's explanation of why we don't know and why that little problem exists.