A “leap second” will be added to the world’s official clocks on Dec. 31 at 23 hours, 59 minutes and 59 seconds Coordinated Universal Time (UTC), which corresponds to 6:59:59 p.m. EST; the clocks will read 23:59:60 before ticking over to midnight. The goal is to keep two different timescales in sync with each other.
So, why is this important to you as an ISP?
The trouble is that even as they use the leap second, UNIX and Linux define a day as something that is unvarying in length. “If a leap second happens, the operating system must somehow prevent the applications from knowing that it’s going on while still handling all the business of an operating system,” says Steve Allen, a programmer with California’s Lick Observatory.
Many patches and fixes have been put in place to adjust for this in most Operating systems. The concern, even a year after the last one, is software that has not been updated to account for dealing with leap seconds.