Hey, wait a second Tiny adjustment being made to today’s length
Tuesday is going to be a longer day than most.
Not much longer. Only a single second will be added to the clock. Around 8 p.m., an extra second called the “leap second” will occur.
“Periodically, we have to adjust our time-keeping to accommodate the fact that the Earth doesn’t actually spin at a set, constant rotation,” said Amanda Holland-Minkley, an associate professor of computing and information studies at Washington & Jefferson College.
The reasoning behind the leap second is not dissimilar from the need for a leap year. To keep our time in line with the Earth’s rotation, time must be added on. So every few years, an extra second is added to the Coordinated Universal Time (UTC). This is important for things such as GPS services, as any discrepancy between the UTC and the atomic clock can render GPS inaccurate. Unlike the leap year, which is on a rigid schedule, the occurrence of the leap second can be erratic. According to Holland-Minkley, a leap second won’t be announced until six months in advance. The last one occurred in 2012, and there was even a six-year gap between 1999 and 2004 when a leap second didn’t happen at all.
While the addition of an extra day for leap years can be handled with relative ease, the sporadic nature of the leap second lends itself to issues with computers being able to process the extra second.
“We know when leap years are going to be forever, we don’t know when the next leap second is going to be. … So when our computer systems are built, they have to be built to accommodate leap seconds, but without knowing when they’re going to happen,” Holland-Minkley said.
The systems that are most at risk are ones that are sharing and distributing information between multiple computers and servers, as well as systems that are made to work as quickly as less than a second. An example of the latter would be the stock market, so some exchanges will pause when the second is due to arrive to avoid potential problems.
“Generally, the visible behavior is that a server will crash. The reason for that is that the server will see the leap second being taken into account and somewhere in its code, it will register that as an error,” Holland-Minkley said.
For most people, the leap second will pass without notice, but people working as network and system administrators will have to ensure their computers handle it properly.