Can U extend B1B2 Expire Date?

My dad got his B1B1 visa couple weeks ago in Guangzhou. He has to leave in 3 months. I wants him to come summer next year when weather it's better. (I know, we didn't thought of that in the beginning). Is it possible to delay his B1B1 expire date at the US consulate? I've searched the http://www.travel.state.gov/ site for a while, but had no luck of finding any info regarding this matter. Thank you very much if you can share your insight.