If you are living in an area which just had daylight saving changes (i.e. Australia), you may find that your Windows Mobile need updating to the new DST rules. Microsoft only seems to provide patches for WM 2005 and up, so unfortunately for those with 2003, you’re left with a confused clock which can’t properly tell when DST begins and ends. Me being an owner of one of these, I scoured the net looking for a way to manually correct this. If you are on normal Windows, there is a utility called tzedit.exe which allows you add change timezone and DST rules. However, it doesn’t look like it exists for the PPC.
In Windows, timezones are stored in the registry and sure enough, same applies to PPC, except it is in a different format. The default registry doesn’t store any timezones and it only reads the registry for overrides. The registry key in which the timezone overrides reside is HKLM\SOFTWARE\Microsoft\Timezones, under that you have put each timezones as a separate key named with a timezone id. Timezone ids are cryptic. 255 corresponds to Sydney for example. A full list is avaliable on the page. Creating a new registry key 255 (or another time zone number) and setting the TZI binary variable to the same value as TZI on a desktop Windows (with correct rules) should allow your PPC to understand the new time zone daylight saving rules.