Easy Way to Replace Content on Page and Transfer it?

Hello all!

I'm working on getting the inner workings of my site running smoothly. Everyday I make a blog post on the site, I want the url for the most recent post to be mysite.com/blog. Then I want to make the old post (the one that used to be at mysite.com/blog) to become mysite.com/blog_date. What is the easiest way to do this? In the olden days I would simply copy the file to my server with the url mystie.com/blog and recopy the old post as mysite.com/blog_date. Can I still do some sort of file transfer swap like this in drupal? My goal is for this to take the least amount of time as possible.

Thanks in advance for your help, I'm sure this has been posted before and I've been trying to search for it but its a tricky thing to word in the search bar for the best results. Alas, I will continue to search while I await all of the guru's insightful replies.