I start an Assistant Professor position in August (in USA). Is it better to hire a Phd in August or January? I start an Assistant Professor position in August at a USA university (ranked between 30th and 70th). I am already advertising the two PhD positions I got in the startup, and for one of the two I already have a list of good candidates, in particular I like a lot a specific candidate. Which one do you think the best move is? Asking the candidate to start in August with me (beginning of fall) or in January (beginning of spring)? Which are the pros or cons? I spoke with the graduate school coordinator and he said both options are possible, I have to choose. And also the candidate said he has no particular preference, he finishes the Master in June and he might do a short internship until December (or take a break and visit family) if he will have to start  with me in January.

Note:
I will hire the second PhD in August 2018, cause it comes from different funds, available only in August of each year, and the deadline for those is past.
Often, your first semester in a faculty position flies by...especially if you are teaching (which you do not mention). You often meet with HR and administrators, learn where everything is on campus, and settle into your new home/hometown (I've started as a new faculty member at two different universities in my career). Consider that you might not have a lot of time to supervise and manage people during your first semester, which will waste your start-up funds. Waiting to hire the candidate in January will give you time to set up your program of research and have a full list of work for the candidate to work on when they start. Just a thought. Congrats on the job!