As is well known, Rosh Chodesh Kislev and Teves are sometimes one day and sometimes two. This causes numerous halachic issues in regards to Bar Mitzvas and yaartzeits. (See also earlier report on TLS.)
In this half-hour shiur delivered to businessmen in Baltimore, Rabbi Dovid Heber explains why the calendar changes from year to year, its halachic implications, and this phenomenon’s connection to Chanukah.