My car changed years and I cant change it back

Hello, I was making a car with a year set to 1993, I was messing around with production and markets tab and it switched to 2012 and it gained 200kg. How do I switch it back to 1993?

Okay, I have changed the car chassis material while looking through the wiki page at the unlock dates section and I managed to put it back to 1993.

OK, good stuff. Unlock dates are very important to heed!

Unlock years also depend on techpool - adding techpool points ensures that a specific part can be chosen sooner. For example, AHS steel as a chassis material is only available from 1996 by default, but increasing the chassis techpool to, say, +7, ensures that it can be unlocked as soon as 1989. Conversely, negative techpool causes you to take longer to unlock a specific part.