If your clock is already set to the right time, the website is likely misconfigured, and there is nothing you can do to resolve the issue. You can notify the website’s administrator about the problem.
Os yw eich cloc eisoes wedi ei osod i'r amser cywir, mwy na thebyg mae'r wefan wedi ei gam osod a does dim fedrwch chi ei wneud i ddatrys y broblem. Gallwch hysbysu gweinyddwr y wefan am y broblem.