Another interesting fact is found 28 miles Northeast of Mexico city, in the great Pyramid of the Sun. It was built by Aztecs and its west face is oriented to the rising (or setting) of the Pleiades. The date of their midnight culmination was observed with solemn ceremony in countries as widely separated in the world as Pre-Columbian Mexico and Ancient Persia. W.T. Olcott suggests that " these universal memorial services commemorate a great cataclysm that occurred in ancient times, causing a great loss of life... " In the middle ages their midnight culmination became the traditional date of the fearsome " Witch Sabbath " or " Black Sabbath ", the night of unholy revelry. The date evidently preserves the memory of the ancient Druid"s rites of November 1st, still observed in the modern world as " All Hallows "eve " or " Halloween ". The traditional date has also been kept, although the actual midnight culmination of the Pleiades now occurs on November 21st.