53 Pa. Stat. § 572
All members of councils and all other city, ward, borough and township officers, excepting school directors, to be elected on the third Tuesday of February next, or in any year thereafter, whose term of office would, under existing laws, expire prior to the first Monday of April, shall continue in office from the date at which said term would otherwise expire, until the First Monday of April next ensuing thereto; and the terms of their successors shall begin on the first Monday of April, and shall continue for the period now fixed for the duration thereof by existing laws in each particular case; and hereafter all elections for office[r]s which will be vacant on the first Monday of April, shall be held on the third Tuesday of February next preceding thereto.
53 P.S. § 572