Building old code and getting the same result is not always trivial to do.

Potential issues:

- If you have content in a database, can you able to restore the database at any point in time?

- If you code has dependencies, were all the dependencies checked in the repository? If not, can you still find the same version you were using.

- What about your tools, compilers, etc.? Sure some of them like Go are pretty good with backward compatibility, but not all of them. Maybe you used a beta version of a tool? You might need to find the same version of the tools you were using. By the way, did you keep track of the versions of your tools, or do you need to guess?

Even with static websites, you can get into trouble if you referenced e.g. a JS file stored somewhere else. But the point is: going back in time is often much easier with static websites.

(Related topic: reproducible builds.)