[CountZero]

I recently grabbed all the issues of Starlog magazine available from the Internet Archive. I've gotten the series, title, and publisher information set up in metadata, and I've manually edited the dates up to the point where the magazine goes to a monthly format. So, from here I'd like to auto-increment the dates to save myself some work, but I don't know how to do so.

Does anyone have any advice on how to do this? Thanks!