Monday, February 1, 2010

Updating DST on Windows CE

In a post coming soon I'll talk about Handheld PCs more, but essentially, I recently rediscovered a 10-year old piece of technology that is a Jornada Handheld PC. Unfortunately, it still has the old United States Daylight Savings Time definitions and apparently no simple way to update them automatically. HPC:Factor has an installable update for Windows CE 4.2 and Microsoft has official updates out for newer versions of Windows CE/Windows Mobile, but I could not find anything for Windows CE 3.0 and older. Eventually, by comparing all the hexadecimal values of the registry modifications made by the HPC:Factor update and the current built-in time zone settings, I was able to come up with an appropriate workaround. While it's a little cumbersome to apply and isn't as permanent (if you change your home city, the time zone definition will be reloaded from built-in settings), it certainly works and I think is sufficient for my needs. Note that this fix assumes your location has always and still does observe DST, but springs forward in March instead of April and falls back in November instead of October now.

To update the rules for the new DST rules:
  1. Control Panel -> World Clock -> Home City -> pick one and stick with it!

  2. Open a registry editor (you will need to install one on your own, Microsoft supplies a PowerToy download if you have trouble finding an editor)

  3. Navigate to HKEY_LOCAL_MACHINE/Time

  4. There should be one binary value, "TimeZoneInformation", at that location. Edit the long sequence so where there was a segment reading "0A 00 00 00 05 00 02" it now reads "0B 00 00 00 01 00 02" and where there was a "03 00 00 00 02 00 02" it now reads "04 00 00 00 01 00 02"

  5. If you want to go back to the old DST settings, just go back to the World Clock Control Panel and change your city. Similarly, you'll need to redo these steps if you change your city.

Keywords: DST, Daylight Savings Time, Windows CE, HPC2000, HPC, HPC/Pro, Jornada

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