On the 1st of January 2000, some people were expecting to see the world crumble because old software applications had been written using dates coded on 2 digits. At the turn of the century (or rather at the change from 99 to 00), there was a need for upgrading/patching applications to support 4-digit years in order to avoid the end of civilisation.
The nightmare did not happen for the world, but there was a boom for the IT industry around the correction of the Y2K bug. Today, we are reaching a point where we could see another similar drama: The Y2K7 bug.
In 2005, the US Congress decided, as part of the Energy Policy Act of 2005, that the date used to switch for Winter times to Summer times and back (in application of Daylight Saving Time) would be changed. Instead of being the usual 1st Sunday of April and the last Sunday of October, these dates would be moved by 3 weeks for the US and a few followers like Australia. This becomes applicable in March 2007.
It wouldn’t be much of a problem if that did not have to be hard-coded in the many software applications using time information. Most of them need to be patched to behave correctly.
Most certainly, any unpatched pre-2005 application is doomed to behave incorrectly next March when time comes to change times. Did you notice that Windows 2000 is still counting as 10-15% of installed Windows PC? Did you notice that Windows XP was launched in 2001? Maybe your calendar application or some airlines reservations software has not yet been updated… As for the Y2K bug, the Y2K7 bug may have influence on more hidden systems: routers, photocopiers, PDA, cell phones, room/conference reservation services, energy metering systems and -of course- the blinking digital clock of our VCR (OK! This last one should first be set to the right time once).
The patch dance should be started by now.
For those really worried about it, Windows XP has already been patched by Windows Update. No need to rush and buy Vista just for this.