July 4, 2012
southburnett.com.au and a number of other South Burnett websites were briefly off air for about 20 minutes this morning when we fell victim to a leap second.
A leap second – as the name suggests – is a one-second adjustment that’s occasionally applied to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time.
The UTC time standard is based on atomic clocks and is widely used for international timekeeping.
However because the duration of a mean solar day is slightly longer than 24 hours, leap-seconds need to be added to UTC occasionally to keep the two in synch.
But because the Earth’s rotation speed varies in response to climatic and geological events, UTC leap seconds (unlike leap years) are irregularly spaced and unpredictable.
This irregularity and unpredictability poses problems in many areas, but particularly with computers, which require absolute precision to operate correctly.
So ever since the latest leap-second adjustment was applied to UTC on June 30, web servers all over the planet have been briefly “going dark” while they were rebooted to adjust to the new UTC time.
It was the South Burnett’s turn this morning …
Footnote:
The need to add a leap seconds to UTC is usually decided about six months in advance by the International Earth Rotation and Reference Systems Service (IERS), who strive to ensure that the difference between the two time standards will never exceed 0.9 seconds.
Between their adoption in 1972 and June 30, 2012, 25 leap seconds have been added.
Leap seconds affect web servers because the Internet is a global network that uses the UTC time standard, but they have no effect on personal computers.
