when do you change the timing belt on a 2007 chevy cobalt ? thanks in advance?

[jjgoetz4]

i have a 2007 chevy cobalt with almost 60000 miles and i'd like to know when to change the timing belt & water pump assembly. thanks in advance.
i should also mention that i do not have the owners manual
thank you robert

 

[Robert]

change it at 100k along with the water pump