Rule 600 is an important rule in seeking a dismissal of a Bucks County criminal case based upon your speedy/prompt trial rights.
The date starts when the criminal complaint is filed, not when the person is arrested. If however, there is delay due to the defendant absonding from justice, this delay may be excludable.
If the Commonwealth has trouble getting their witnesses and affiants together for a case (i.e. the officer is in training, on vacation), this time is generally ruled "includable" and counted towards the 365 days.
If the court hears a Rule 600 motion and find that the Commonwealth exercised proper due diligence regarding the timeline and that the circumstances involving the postponement were beyond the control of the Commmonwealth, the motions to dismissed will be denied.