How long do you need to train for a marathon?

I want to do one in 4 months. I don't have the best running base, my longest run has been 8 miles. I got the idea this morning to do a marathon, and I picked this one in 4 months.Any thoughts?|||You should be able to train for one in 4 months go to www.runnersworld.com. They have a great program that designs to your pace also great tips on traing, nutrition and a lot more. The program is free and it ranges from the beginner to the Elite runner|||Well, you are already able to run a good distance so i guess four months will be fine. Why not download a training plan so that you can build up your distance gradually. After all, you only have to finish...the time is secondary. You need to commit to the training until your event...best luck x