First, make sure on the homepage you see GMT-8. If not, that means your time zone change is not correctly saved.
If that’s correct, then it might be that your router is blocking the NTP sync port 123 for some reason. OpenSprinkler uses the NTP server at 126.96.36.199 by default. If you have a linux machine, try to run the following command:
nmap -p 123 -sT 188.8.131.52
and see if it reports the port is open. If not, you may have to change corresponding settings on your router to see if you can unblock the port.