A weekly feature of Torah Tidbits to help clarify practical and conceptual aspects of the Jewish Calendar, thereby better fulfilling the mitzva of HaChodesh HaZeh Lachem...
Chanuka is the only holiday that spans two months. That means, of course, that Rosh Chodesh Tevet falls during Chanuka. On the 6th day, to be specific, and on the 7th if there are two days Rosh Chodesh (which there usually are, but not this year). Kislev's usual number of days is 30, which it has during an "in order" type of year and in a "full" year. Only in a "deficient" type of year, in which a day is removed, leaving 353 days in a 12-month year or 383 in a 13-month, 2 Adar year (such as this one - 5765). The day that is dropped in a CHASEIR is the 30th of Kislev. Years are CHASEIR (353/383) 25½% of the time. K'SEDER (354/384) 29½% of the time, and SHALEIM (355/385) 45%. Note that "normal" is not most common - "full" is. There is no Yom Kippur Katan for Rosh Chodesh Tevet because it would fall during Chanuka.