It makes sense to start with the year zero when you want to do any calculations that involve dates that where before and after year one.
If an empire was founded in 50 BC and dissolved in 50 CE to calculate its age when it was dissolved you have to acknowledge that there is no year zero so instead of just calculating 50 - (-50) = 100 you have to substract one which is counter intuitive. Because it went from year 1 BC straight to 1 CE.
By that part, I was referring to the people establishing the Julian Calendar, not the Gregorian. I’ve edited my comment to clarify that.
Removed by mod
It makes sense to start with the year zero when you want to do any calculations that involve dates that where before and after year one. If an empire was founded in 50 BC and dissolved in 50 CE to calculate its age when it was dissolved you have to acknowledge that there is no year zero so instead of just calculating 50 - (-50) = 100 you have to substract one which is counter intuitive. Because it went from year 1 BC straight to 1 CE.
Removed by mod