Ketaki,
Well it's always a good idea to look at the school averages to give you an idea of what sort of candidate they are looking for. So Harvard and Stanford may be looking for younger candidates, (still with a bit more experience), but other schools look for more experienced. Also keep in mind than the average months worked is usually calculated from the date not of admission, but from when the program starts, which means that you'll have another year, bringing you closer to the average. Finally, the concern is less the "technical number" of how many months, as it is the experience that this will allow you to gain, and the stories you can get out of it. So, people with one or two years of experience, usually don;t have such strong stories because of the nature of first-year jobs. But if you DO have those stories, then you are in much better shape.