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. [The Best "Star Wars" Ships from a Galaxy Far, Far Away]
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.