The Ancient Jewish Calendar

Today, we have a set Jewish calendar that has been in use for the past 1700 years. However, for the first 1600 years or so of Judaism, we used a variable calendar that was updated monthly based on sightings of the new moon and calculations made by the Sanhedrin, the Supreme Council of Judaism.  A fascinating class about Kiddush Hachodesh, the system used for the ancient Jewish calendar.