北京 Parents visiting 簽約到幾號了？

Should that be B1 or B2?
I want to schedule an interview for my parents in early September. When should
I call? Have someone called them recently and what's the dates available now?
Thank you so much.
Another question: I believe the number I should call from USA is
86-21-3881-4611.Does that mean I should call by China time? What's their
office hours?
So sad for knowing so less.
Thanks for any help.