In the first flashback, which takes place around 2008, Agent May mentions that S.H.I.E.L.D. is putting every dime into the construction of the Triskelion, as seen in Captain America: The Winter Soldier (2014). However, at the beginning of Ant-Man (2015), the Triskelion was already under construction, and that sequence took place in 1989, so she was probably referring to the addition of the underground hangars and the three Helicarriers for Project Insight (also seen in The Winter Soldier).
Skye's birthday is revealed to be July 2, 1988. At this, Skye realizes that she's 26, setting this episode in late 2014 or early 2015 (likely early 2015, given the airdate). Chloe Bennet was four days shy of 23 when the episode premiered.
"Melinda" originally aired on ABC on April 14, 2015, and according to Nielsen Media Research, was watched by 4.04 million viewers.