The Basic Officer Training Course (BOTC) is made up of two courses: Initial Assessment Period (IAP) and Basic Officer Training Period (BOTP). I think it always starts very late April or the first few days of May. The whole thing was 10.5 weeks when I did it, I think the Reg Force Course takes 14 weeks. Both courses cover the same material, but the the NAVRES version compresses the same material into a shorter time. There was talk of lengthening the course this year, I do not know if they have done that, but your unit should have course scheduling available by now.
When a NCdt gets commissioned depends on the entry plan: if you have a degree, you would be DEO, and are an A/SLt at the end of BOTC, probably retroactive to the date you joined (keep that tidbit in mind for pay purposes, by the way... if you are DEO, your joining paperwork probably has you joining as a NCdt, promoted to A/SLt the same day, but you are not paid at A/SLt or permitted to wear the rank until you pass basic... then you get the difference in pay retroactive to when you joined, in one lump). If you are working on a degree, you are probably RESO, and once finished basic, you stay a Naval Cadet until the earlier of when you are MOC qualified or you finish your degree. Possibly you might get your commission after MARS III, but I am DEO so I never looked into that.
I won't get my SLt's until I have MARS IV, which is why I wonder if maybe you get your A/SLt after MARS III, or maybe get commissioned as a SLt when done MARS IV. I'm not sure how getting the degree plays in at this point. Anyone else know for sure?