I recently was accepted into a Ph.D. program to begin in the Fall---I receive my Bachelor's degree this weekend. I wanted to know when would it be considered acceptable to start calling myself a graduate student? For example, when is it appropriate to change my LinkedIn and ResearchGate profiles (and my CV) to read "Graduate Student" at the institution in question? I asked my program director, but all he said was that I "was definitely accepted into the program." I want to update my status on my resume and online profiles to reflect this new position, but I don't want to be rude. What should I do?
You're not really a student at your new institution until you have actually arrived and registered there. At this point, it would appropriate to say something like:
I will be a graduate student at Institute X with anticipated start date D
You can certainly update your CV to convey that information immediately.
As for other sites, typically they allow you to list a number of positions with starting and ending dates. If their system lets you list a start date in the future (I haven't tried that on the particular sites you mention), then that would be a clear enough communication of your current and anticipated status. Otherwise, you can write the same sort of "anticipated start date" line in your free-text personal description.