A 2000 Chevy S10 does not have a timing belt.
The 2000 Chevy Trail Blazer doesn't have a timing belt.
Change it every 100,000 miles.
That truck does not have a timing belt. It has a timing chain that will last the life of the engine.
The SC2 is an 'S' series Saturn, and all 4 cylinder engines of the S series Saturn's used a timing CHAIN rather than a timing belt.
The 4 cylinder Saturn engines used an "Oil bath" timing chain. The V6 Saturn engines used an "external" timing belt.
According to the owners manual, for that vehicle the timing belt should be changed at 110,000 miles.
90,000 miles or 10 years.
The timing belt should be replaced every 100,000 miles.
It should be replaced when it begins making a noticeable noise.