Vectra timing belt

My wife?s 2005 Holden Vectra 2.2-litre four-cylinder is up to its 60,000 km service, and looking in the service manual it does not state any service for the timing belt to be done. It only states for the 3.2-litre V6, which is to be changed at 120,000 km. I have heard it needs to be done at 60,000 and 120,000 km. What is correct?