That would make things a bit difficult, so you might have to leave the job ultimately - somewhere in August 2016 I suppose. In the meanwhile just acquaint yourself with all the subjects, and preferably start preparing 1. See how it feels. See if you really enjoy it even after a month, and if you feel good you're a good candidate for the exams.

And apply for the PMS exams that's just been advertised. Just appear. You'll have a full-dress rehearsal of what the CSS exams would look like. You can apply by the end of this month and the exams are somewhere in December2015-January2016.

PS: If you work 5 days a week, you can do without leaving your job. May be a leave for a month or 2, if possible, would do.

Disclaimer: This post represents the opinion of a person not competent to speak on issues pertaining to persons in job. Take his advice with a pinch of salt.