When I was younger, “launch dates” were exactly that: the day upon which you'd go to the store and, assuming the shipment had arrived on time, pick up your box. The glorious digital future has granted us a much greater degree of precision for such things, however. These days, we have not just dates, but specific times—to the very minute!—when games will become playable.
Take Overwatch, for instance. We've known for quite awhile now that it will go live on May 24, but today Blizzard revealed that date applies only in Europe: North American gamers will be able to get their hands on it as early as 4 pm PDT, or 7 pm EDT, on May 23. Overwatchers in the Asia/Pacific part of the world, on the other hand, will have to wait until as late as 9 am AEST (that's Australia) before the fun begins.
Here's the full schedule, complete with a map that's not really helpful but far too swanky to leave out: