The answer for last time with 2 walkoffs:
July 31, 1983.
Jesse Orosco won both games for the Mets against the Pirates. Bob Bailor drove in Darryl Strawberry to walk-off G1. George Foster drove in Mookie Wilson to end G2.
Without walkoffs:
Chase Shugart is the 1st pitcher to earn 2 wins on the same day since Brian Duensing did so for the Twins on Aug. 9, 2013.
First Phillies pitcher to do so since Terry Adams on Sept. 21, 2002 vs. the Reds.