I just tried ‘Adelaide, Australia’ and it works fine: the firmware is able to find out it’s UTC+9:30 time zone, and the device time is shown correctly. Note that after you set the time zone, there will be up to 15 seconds delay before the updates are shown in the UI. Also make sure your OpenSprinkler is connected to a router that can reach the Internet, for the obvious reason that it needs to get data from the Internet.
If it still doesn’t work, you can manually try the url below:
http://rayshobby.net/scripts/weather.py?loc=Adelaide,Australia
This is the script that the firmware uses to calculate timezone, sunrise and sunset time (and also water percentage if a WUnderground API key is provided). My output currently contains the following:
tz=86&sunrise=347&sunset=1101