A new official Star Wars timeline released by Random House/Del Rey has plotted out when exactly Solo: A Star Wars Story takes place - and how it fits in relation to Rogue One, the prequel trilogy, and even pre-A New Hope prose novels.
Solo is set to take place roughly 11 to 14 years before A New Hope's Battle of Yavin (BBY for short). Rogue One primarily took place days before A New Hope, although the early flashback with Galen Erso and his family is 13 BBY.
Another new addition to the timeline is the upcoming prose novel Star Wars: Last Shot, set immediately prior to Solo.. Scheduled for release April 17, Last Shot's description reveals that the pilots of the Millennium Falcon are Lando Calrissiain and L3-37 but lists Han Solo and Chewbacca as merely crewmates.
You can view this updated Star Wars timeline here: http://www.randomhousebooks.com/campaign/star-wars-timeline/
Solo: A Star Wars Story opens in theaters May 25.