What does Date Created in Finder mean?
In most cases, "Date Created" is the date you created the file. For example, if you write a document and save it, "Today" is the creation date.

If I check my Applications folder, I can see that "App Store.app" was created on June 18, 2015. However, it's impossible for it to have been installed on that date because I installed El Capitan on the USB drive I'm currently booted from just a couple weeks ago (in other words, in June 2015 I didn't own a bootable copy of El Capitan). This means that the "Date Created" was the date that the app itself was created and not when it was installed.

In some other cases (I can't find the file I'm thinking about right now but if I do I'll edit my answer) you can download files and they could retain their metadata. You can download a file created years before you even owned your computer. If the metadata is retained you could have a creation date that is before your owning of that computer (e.g. download a document written in 2013 on a 2014 laptop).