Does defendant have served his sentence in his drug possession case while he is serving time in his domestic violence case?

This court requested supplemental briefing on the issue of whether defendant had in fact completed serving his sentence in his drug possession case although he was still incarcerated for his domestic violence case. We agree with defendant and the People that the trial court correctly designated defendant's felony conviction in the drug possession case to be a misdemeanor under the provisions of section 1170.18, subdivisions (f) and (g). As both parties point out, defendant's credits covered the majority of his two-year sentence. And "[a] concurrent term . . . begins on the day it is imposed and is not postponed." (People v. Bruner (1995) 9 Cal.4th 1178, 1182, fn. 3.) Additionally, since defendant was sentenced to concurrent terms, his concurrent terms did not merge into a single aggregate term as would have been the case if he had been sentenced consecutively. (In re Reeves (2005) 35 Cal.4th 765, 773.) By the time he filed his application, he had already completed serving his sentence in the drug case. Therefore, the trial court had no jurisdiction to resentence him in the drug case, and, correspondingly, the court had no jurisdiction to resentence him in the domestic violence case.