Assuming you have completed aoll of the requirements and conditions of parole, it is over at midnight of the last day of the sentence. The Commonwealth can still file a violation petition after that date if you have violated parole prior to that date.
It would be midnight but I believe there is a split in Pennsylvania law regarding whether the prosecutor can pursue a violation of parole after completion of the parole, when the violation occurred during parole. See CW v. Smith 860 A2d 142 (Pa Super 2004) which hurts your position and CW v Karth, 994 A.2d 606 (Pa. Super 2010) which states that a violation cannot be commenced after the parole end date.
Please note that I am only licensed in Pennsylvania. Therefore, if your case involves another jurisdiction, you should disregard this post. Further, this posting does not constitute proper legal advice since I have not been able to learn all the circumstances of your case. As such, you should consult a lawyer in person immediately for proper legal advice and should not rely on this posting for legal advice.