“Overwatch’s” Physical Copies Release a Day Early
Servers Won't Launch Until 24th, Though
According to those who ordered physical copies of "Overwatch" from Amazon (such as Destructoid), the physical versions of "Overwatch" will release one day earlier than the digital versions.
GameSpot got confirmation from Blizzard that retailers with physical copies of "Overwatch," such as Best Buy and GameStop, will get the game a day early.
The reason for the day early release is to get everyone ready for the game when the servers go live. Take note that the servers aren't launching early - that date is still May 24, 2016. Those who pre-ordered the game digitally may pre-load the game so they don't have to worry about downloading on the day the servers launch.
Source: Destructoid GameSpot