How long does it take for gas to go bad?

i have a 96 galant that has been sitting for about 8 or 9 months. its got about half a tank. im low on funds and need gas for my car that i use. the galant broke down. something about the valves being bent. so yeah. id liek to siphon the gas from my galant and use it for my honda accord. how long does it take for sitting gas to go bad. oh by the way its regular unleaded. thanks in advanced.