http://www.smogtips.com/frequentlyaskedquestions.cfm#SmogCheckReg4 said:
Effective 04/01/05: Under the old law, 1975 and subsequent model year vehicles became exempt from Smog Check when they turned 30 years old. A 1976 model year vehicle was exempt in 2005, a 1977 in 2006, etc.
Under the new law... commenced April 1, 2005, exempt from smog check requirements are any motor vehicle manufactured prior to the 1976 model-year. All vehicles 1976 and newer vehicles will be tested according to state emission law. This law repeals the 30-year rolling exemption.