If you join before you complete your degree, you will have to join the enlisted side. If you are set on officer only, you will have to wait until just before you finish your degree. So, my suggestion would be to wait until after the 1st of the year to start the process.
"If being an egomaniac means I believe in what I do and in my art or music, then in that respect you can call me that... I believe in what I do, and I'll say it." - John Lennon