We’re into March, and Daylight Savings Time is coming earlier this year thanks to the Energy Policy Act of 2005.   (for most of the US and Canada anyway.  Folks in Saskatchewan can probably skip the rest of this post).  For anyone not up to speed, starting in the spring of 2007, daylight saving time (DST) start and end dates are changing. DST dates in the United States will start three weeks earlier (2:00 A.M. on the second Sunday in March) and will end one week later (2:00 A.M. on the first Sunday in November).  In order to prevent ripping the fabric of the space-time continuum and other general chaos, Canada has decided to follow suit.

So, the million dollar question is ‘What does this mean for OPC products?’.  Well, for the actual data transfer between OPC clients and servers, it doesn’t mean anything.  All timestamps used by OPC are specified as UTC (Universal Time Coordinated), so are unaffected by timezones and daylight savings time.  However, OPC clients and other applications rarely display timestamps as UTC.  Typically the OPC client will use the system time to convert between UTC and the local time.  Therefore any application that uses the Windows system time (including OPC products) should be patched so the new DST rules are taken into account.

Those of you using Automatic Updates are probably patched already, but many OPC products are running on production machines that don’t get auto-updated.   Information on the DST patch can be found in Microsoft’s KB931836 (which supersedes and replaces update 928388, released in November 2006).   So, if you haven’t done so already, get your systems updated.  The time is quickly approaching.   (or at least due to the curvature of the space-time continuum, as three-dimensional beings, we infer the existence of the fourth dimension of time as a linear form.)  

Interestingly, a dimension does not need to be detected to exist. If we had no memory of the interval we label as “time,” our existence in space/time would still occur.  Kind of like even though you don’t remember the copious Tequila shooters and the ensuing incident with the donkey, trampoline and floral lederhosen, doesn’t mean it didn’t really happen.  Keep that in mind.  The more we know, the better decisions we’ll make.