It depends on a lot of things. Can you read sheet music? Have you played an instrument before? Are you willing and able to dedicate practice time? Can you afford a teacher? Do you have a piano?
Also, different people progress at different rates - it takes some people years, others a few months.
The piano also involves 2 different clefs, and hands doing different things at the same time - obvious, maybe, I know. I should also point out that no instrument is easy to learn.
You would not be able to take an exam with ABRSM exam board before October - their session is November - December, and results take 2-3 weeks.
However, like the above person said, I feel it would be better gleaning experience and enthusiasm for your subject, than trying to get Grade 1 piano, just to put it on your form/impress interviewers.