Unity only changes some of the files, here is a good thread: https://answers.unity.com/questions/12341/date-of-exe-build-is-not-correct.html
I've also added a screenshot of the top 2 games. (blue: actual date, red: wrong date) The red marked date is presumably the installation date of unity, and all the data of an new project are stored in the data file, so the others won't change.
In this case, its not the fault of the creators, but of unity.