Microsoft wants to add one extra second to Windows, starting with Windows 10 Redstone 5 and Windows Server 2019. With the upcoming updates for Windows 10, Microsoft's operating system now deals with leap seconds in a way that is incredibly accurate, UTC-compliant, and traceable.
For those who did not know, leap seconds typically occur every 18 months, resulting in one extra second. The extra leap second occurs to adjust with the earth's slowed down rotation, and an extra second is added to UTC in order to keep it in-sync with mean solar time. To deal with the extra second more appropriately, Windows 10 will now display that extra second, instead of directly jumping to the next one.
The new move makes Windows Server the first OS to have full support of the rare but valid timestamp of: 23:59:60. Linus Torvalds has long maintained that users needs to chill out about leap seconds, but then again we have never noticed Linus to chill out about much.