Where to check/how to get original post publish date?

Hi,

How can I find out when a post was first/originally published? I re-publish on my blog often and because there are a large number of Contributors I need to check who is active and who is not, so I want to see when a post was first published. I’m not an expert in PHP, and would NOT want the original post date to be displayed on the front end, just in the back-end for admins to see.

Thanks!