Christmas is not mentioned in the Hebrew calendar. Christmas is a fixed date in the Gregorian calendar year. The Hebrew calendar lists important dates and holidays to the Jewish people, and follows a lunar calendar cycle.
Christmas is widely regarded as an important Christian holiday. Although many Jewish people celebrate a secular form of Christmas, the only holiday occurring around the same time as Christmas listed on the Hebrew calendar is Hanukkah. Hanukkah starts on the 25th day of Kislev, and is not a Jewish form of Christmas. Jewish holidays and important dates do not appear to have a fixed date on the Gregorian calendar because the Hebrew calendar is a lunar calendar.