how do i set clock on jvc car radio kd-sx830?

Answer 1

Try this:
press and hold the "SEL" button for more then 5 seconds..
Using the FF or REW buttons select "Clock H" turn the volume knob to set.
Using the FF or REW buttons select "Clock M" turn the volume knob to set
Press the "DISP" button to start the clock.

I hope that is correct. I could not find the KD-SX830 but a 838 and most manufactures keep the same operations across the line of equipment.

If that doesn't work then goto http://books.jvcservice.com/ and try to find another model close to yours.