how do i calculate or convert dates from the gregorian calendar to the julian calendar?

by heisenberger

I am trying to figure out what the date of eruption of vesuvius would be (we'll use 24 august, 79 CE) in the julian calendar, including year. the date would be IX kal. Sept. I think. but what about the year.

What would the date be a month before (24 July 79 CE)?

KNHaw

There's a general calendar converter here and a Julian specific converter here. Also, Wolfram Alpha is also a great source for general questions like this.