Im a bit surprised that I haven’t heard more about this (perhaps the hysteria will whip up as we get closer to the date). The gist of it is that with the newly enacted Daylight Savings Time (DST) guidelines older Java Virtual Machines (JVMs) will not adjust for DST properly starting in 2007. The first event will happen on March 11, 2007.
If you have been looking for a reason to upgrade to JVM 1.5, this should do.