display date with offset

Hi,
I searched for a plugin that renders the date with a customized offset.
So I would like to use the regular date in the backend, but everything rendered on the frontend should show the date and time with an offset. Lets say add 120 years.
So all writen articles should show date+120 years. The archive should show date+120 years and so on.

Do you know a plugin to do something like that? Or is there probably a different solution?
thanks