Most of yesterday I spent on implementing proper time zone selection on aprs.fi. You can now select whichever local time zone you wish using a (hopefully) user friendly map tool.
Click on Preferences (on the right side of the real-time map), select the Units and time tab, and click the Change button next to the currently selected time zone. That'll bring up the new time zone selection tool.
Point the mouse roughly at your location (the state or country which uses your preferred time zone), click, click Save to return to the main Preferences view, and click Save again.
You can also select either the time zone or country from the drop-down menus. Or, if browser geolocation works for you, click the I'm Feeling Lucky button. It's not very accurate (I'm being placed in Moscow for example), but it probably works for more than 90% of the population.
I didn't do all of this from scratch - I copy with pride. Thanks go to these two excellent open source projects: timezonepicker and TimezoneJS.Date