In California, 1975 and older cars are currently exempt from smog checks. The law used to be rolling in that cars 30 years old are smog check exempt. They changed the law sometime around 2005 and froze it for 1975 and older. Here is the link to DMV website:
Here is some text from the website:
Does my vehicle qualify for a smog exemption?
Smog inspections are required unless your vehicle is:
Gasoline powered 1975 year model or older