Shabbat_clock Shabbat clock or Shabbat timer () is a time switch programmed before Shabbat (the Jewish Sabbath) or Yom Tov (Jewish festivals) to perform activities prohibited on Shabbat without violating Shabbat. The device operates on a time switch connected to an electrical system and programmed before Shabbat begins. "Shabbat clock" is used to describe any device programmed to operate an electrical device on a time delay, regardless of the reason for doing this.