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The longest day of winter

If you're feeling just a little more tired than usual today -- it's probably because you're feeling the effects of the extra second that was added to the world's clocks over the weekend.

Cue Tui's ad.

The reality is that this leap-second, which was added to keep the world's clocks in sync with the rotation of the earth, went unnoticed by you and I but it did apparently cause some issues for a few hi-tech systems.

One of the biggest victims of this leap-second were Java-based systems -- although there are reports that some Linux-based systems were also jarred into failure by the sudden appearance of a 61-second minute.

Since leap-seconds are nothing new, you'd have thought that a method for handling them would have long-been a standard part of today's OSes and computer environments -- yet apparently, it is not.

Because the time taken for the earth to revolve is not exactly 24 hours (and due to the effect of tidal drag from the moon, the rotation is actually slowing), "keepers of the time" have added leap-seconds that total almost a whole extra half-minute during the past 40 years or so.

Interestingly enough, Google has been smart enough to factor in leap seconds by using an alternative strategy...

Instead of using a 61-second minute and adjusting the clocks of its systems in one abrupt step (with the resultant risks), the search-giant has implemented a strategy it calls "leap smear" -- where far more frequent "micro-adjustments" are made. Instead of a single big jump, many, many micro-jumps of just a few milliseconds are performed over a protracted period ahead of any leap-second.

Of course totally stand-alone systems need not worry about things such as leap-seconds -- their realtime clocks tend to drift by far more than a second or so every month and since they have no other frames of reference -- they continue unaffected -- in a state of temporal isolation.

The real problem arises when computers must talk to each other using protocols which are heavily reliant on accurate temporal synchronisation. The effect of a computer or computers appearing to operate "in the future" can be devastating to the integrity of a network if such contingencies are not properly catered for.

Let's hope that this is the last time programmers are caught unawares by the evil leap-second.

Next time they really ought to know better.

Now all we have to worry about is the Y3K bug -- right?

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