Is the Leap Second 2015 a danger like Y2K?

Many IT companies are dreading over the leap second 2015. Most of these companies are considering the leap second as another Y2K-like bug. However, a recent blog on MSDN clears the air saying that leap second 2015 that is coming on June 30th is not a severe problem like Y2K and it will be taken care by most of the IT companies like Microsoft and Google.

Leap Second 2015

What is Leap Second 2015

The concept behind a leap second and a leap year is same. It is basically a one-second adjustment done to the UTC or the Universal Time to match the days’ time adjacent to the mean solar time. Sometimes, due to climatic changes or natural events like earthquake, earth’s rotation varies. This directly affects the mean solar time. In order to match this irregular time, the leap seconds of UTC are made irregular and hence they become, slightly unpredictable. In simple words, when the event like leap second occurs, the UTC system’s clock can tick a second at any time, to adjust that extra second.

The event of leap second hasn’t appeared for the first time. The last time it appeared was the year 2012. And this year it is going to occur on June 30th. The extra second will be inserted in the UTC at 23:59:60. IERS or the International Earth Rotation Service measures the earth’s rotation and makes sure if it is in sync with UTC. If it is delayed than UTC, then IERS decides when to insert a leap second to UTC. Generally, the leap second is inserted at the end of June or December and at UTC midnight. This time also, it is going to take place at the end of June.

Why everyone is worried about the Leap Second 2015

Basically, it is not the Leap second 2015; but it is the effect that this leap second might have on the computers and software that people are worried about. IT companies are even calling this extra second as the leap second bug. As per their prediction, the software cycle will go haywire due to this extra second and the program may respond in an unpredictable way; as it might misinterpret the leap second.

The leap second will appear as follows:

  1. 2015-06-30 23.59.57
  2. 2015-06-30 23.59.58
  3. 2015-06-30 23.59.59
  4. 2015-06-30 23.59.60 <– leap second
  5. 2015-07-01 00.00.00

So basically, when the clock completes the 3rd step, it should go to 5th step mentioned in above list. However, an extra second is inserted and that makes as 1 extra leap second. And people are worried that the software programs, internet and computer’s system clock will the 4th and 5th step as same and will overlap the procedures.

Read: How does Windows computer react to the extra Leap Second added.

Synchronize the computer clock with the internet time server

You can synchronize the computer clock with the internet time server, as follows:

  • Open Date and Time by clicking the Start button Picture of the Start button, clicking Control Panel, clicking Clock, Language, and Region, and then clicking Date and Time.
  • Click the Internet Time tab, and then click Change settings. Administrator permission required If you’re prompted for an administrator password or confirmation, type the password or provide confirmation.
  • Select the check box next to Synchronize with an Internet time server, select a time server, and then click OK.

Microsoft has assured its users that Leap Second 2015 is certainly not like the Y2K bug which had the potential to create a havoc in the computer’s system.

Posted by on , in Category Windows with Tags
Anand Khanse is the Admin of, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.


  1. Dan

    Unless I’m missing something, seems any pc/device that’s off or at least offline at the precise moment of leap second would be least affected, whereas any, if any, potential for leap second mischief would affect devices online (particularly servers that need 24/7/365 uptime…ATMs, hospitals, emergency services, for example). Thanks, your reminder is appreciated…cheers!

  2. jensenjs

    There are no legal comparison with the y2k problem.

    Y2k was about starting all over, this is only a matter of one second delay.

    Y2k could stop badly computers/figuration (serious)
    Y2K could make servers go down and wait for a fix (serious)
    Y2K could cost millions if not billions or more for the monetary system (Serious)
    Y2K could be a risk for hospitals and others like (Serious)
    But the lap second can be dealt with, just by holding banking back for, yes a second or two. And just for safety the same for hospitals, maybe for a 1-3 days

    This is of course just a wild guess, but never the less a qualified one 🙂

    I was working with the Y2K problem in 1998-jan 2000

  3. Alejandro Zalazar

    Leap second could make servers go down and wait for a fix also, it happened before, and will happen again if no actions are taken to prevent it

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