THANK YOU! I have a 2018 Santa Fe XL - same clock problem. Tried several of the other solutions above but no luck. I followed your method above exactly as you laid it out - and it worked!SD card removal solution worked for me. I have a 2015 Sonata with Canadian firmware. Here’s what I did:
(1) First I moved the car outside the garage so it has access to GPS satellites
(2) Made sure that under Settings -> Clock that the GPS Time is set to ON
(3) Shut off the engine and wait for everything to power off ( lights, radio, etc).
(4) Remove the SD card by pushing it in and pulling it out ( I had to remove the SD slot protective cover first). Wait a few seconds and then push it back in the slot.
(5) Press the start button to turn on the power (no need to start the engine). A message will be displayed saying that the SD card has been inserted and the system will be reset.
(6) Wait for reboot to complete. The clock will still show —:— right after the reboot but wait an additional 30 seconds to a minute for the GPS time to be acquired. Once GPS time is acquired, the dash clock time will also be synced.