JEWS OFTEN SAY..."THE HOLIDAYS ARE LATE THIS YEAR" OR "THE HOLIDAYS ARE EARLY THIS YEAR."

The Holidays never are early or late; they are always on time, according to the Jewish calendar.

The list of the Hebrew months (below) and the holidays that occur during these months also indicates the corresponding secular months.

Hebrew Months    Jewish Holidays                                                                                Secular Months

Nisan                    Passover, Yom HaShoah                                                                    March-April
Iyar                       Yom HaZikaron, Yom HaAtzmaut, Lag BaOmer                                 April-May
Sivan                    Shavuot                                                                                             May-June
Tammuz                                                                                                                          June-July
Av                         Tishah B’Av                                                                                        July-August
Elul                                                                                                                                August-September
Tishri                    Selichot, Rosh HaShanah, Yom Kippur, Sukkot, Simchat Torah        September-October
Cheshvan                                                                                                                       October-November
Kislev                    Hanukkah                                                                                         November-December
Tevet                                                                                                                              December-January
Sh'vat                    Tu B'Shvat                                                                                        January-February
Adar                       Purim                                                                                               February-March

Unlike the Gregorian (civil) calendar, which is based on the sun (solar), the Jewish calendar is based primarily on the moon (lunar), with periodic adjustments made to account for the differences between the solar and lunar cycles. Therefore, the Jewish calendar might be described as both solar and lunar. The moon takes an average of twenty-nine and one-half days to complete its cycle; twelve lunar months equal 354 days. A solar year is 365 1/4 days. There is a difference of eleven days per year. To ensure that the Jewish holidays always fall in the proper season, an extra month is added to the Hebrew calendar seven times out of every nineteen years. If this were not done, the fall harvest festival of Sukkot, for instance, would sometimes be celebrated in the summer, or the spring holiday of Passover would sometimes occur in the winter.

Jewish days are reckoned from sunset to sunset rather than from dawn or midnight. The basis for this is biblical. In the story of Creation (Genesis 1), each day concludes with the phrase: "And there was evening and there was morning. . ." Since evening is mentioned first, the ancient rabbis concluded that in a day evening precedes morning.

For the counting of months, Nisan—the month that begins spring—is considered the first. However, the Jewish year is reckoned from the month of Tishri--the month that begins autumn. This would seem to be the superimposition of one calendar system upon another, which took place during the Babylonian Exile (sixth pre-Christian century).

According to Jewish tradition, history is reckoned from the time of Creation; Jewish years, therefore, are numbered from then. For instance, Israel declared its independence on 5 Iyar 5708 (corresponding to May 14, 1948). The year 5708 (and every Jewish year) was figured by commencing the count from the beginning of Genesis.

Christian custom has been to divide history into two periods: before the time of Jesus (called B.C. = before Christ) and after Jesus' birth (called A.D. = anno Domini = in the year of the Lord). Jewish books generally refer to these periods as B.C.E. (before the common era) and C.E. (of the common era).

The subject of the calendar is rather complex. We have, therefore, touched only its broadest outlines. See more...

Source:  Every Person's Guide to Judaism