Ant-Man and The Wasp shows a few notable scenes before the film ends. We see Scott and Hope enjoying a drive-in movie with Scott's daughter Cassie, and we see Hank and Janet go to a beach, where Hank unveils their old home, shrunken down and hidden in a box. He then goes to grow the house to its normal size.
At the very least, it seems like a few days have passed between Scott being freed from house arrest and Hank and Janet's visit to the beach to reconnect.
Then... the first Post-Credits sequence comes up. It clearly implies that more time has passed, as everyone is back together and Hank has reconfigured his quantum tunnel so that it fits in the back of Luis' van. Scott then goes into the quantum tunnel and travels to the Quantum Realm where he is trying to acquire some healing quantum energy so that they could bring it back and continue to aid Ghost, who apparently was not permanently cured of her quantum dis-alignment that Janet seemed to heal her from earlier in the film.
While Scott is in the Quantum Realm, however, Hank, Janet and Hope all vanish into dust. The "snappening" has now occurred and Ant-Man and The Wasp has now officially caught up to the timeline of Avengers: Infinity War, as Thanos has now eliminated half the population of the universe.
First off, there is a debate over whether Scott, Hank, Janet and Hope should have been doing experiments in the first place, as the ending of Avengers: Infinity War was preceded by an alien invasion of Earth, so you would think that that would have gotten the attention of our heroes. However, even if you wish to argue that they weren't aware of the invasion somehow, it still does not seem to line up with the other heroes explaining that Scott is under house arrest at the beginning of Avengers: Infinity War to him spending a week or two after his house arrest ended at the end of Ant-Man and The Wasp.
We suppose that you could argue that the other "Secret Avengers" simply did not know when Scott's house arrest ended and it was actually already over when the events of Avengers: Infinity War began. Or perhaps Avengers: Infinity War took longer than is appeared. Or the ending of Ant-Man and the Wasp was a lot more condensed. No matter what, though, the timeline looks more than a bit fuzzy.
In theaters now, director Peyton Reed’s Ant-Man and The Wasp stars Paul Rudd, Evangeline Lilly, Bobby Cannavale, Michael Peña, Tip “T.I.” Harris, Judy Greer, David Dastmalchian, Michael Douglas, Michelle Pfeiffer, Laurence Fishburne, Hannah John-Kamen, Randall Park and Walton Goggins.