Moon Musings, the Hebrew Calendar, and "Why ZMANIM"- Part 1

9 Tevet 5776

by Rabbi Daria

Have you noticed that I've regularly been asking if you have noticed the moon?  Why such repetition?  Have I nothing better to say at the beginning of a message to you?  Indeed, this repetition has been very purposeful.  The Hebrew calendar is a luni-solar calendar (as opposed to a purely lunar calendar, such as the Moslem calendar) or a purely solar calendar, such as our civic calendar. As such, the rhythm of the days, weeks, months and years in the Hebrew calendar is highly attuned to our relationship to these two great planets.  Or at least it is on paper. 

In a purely lunar calendar, the months move through the seasons, so that sometimes a particular month will fall in the summer, and sometimes in the winter.  For those who have Moslem friends they may have noticed that sometimes the fast of Ramadan falls during the summer, when the daylight hours are long, and sometimes in the fall, winter, or spring.  I imagine it makes a big difference in the experience of the fast when it lasts for hours longer!

In our purely solar civic calendar we just need to know that when the sun rises a new day starts on our calendar, and after a certain number of days (30-31 most months) the name of the month changes.  Holidays are set in the particular months, and we celebrate what's on the calendar.

In the Hebrew luni-solar calendar we see a combination of these two orientations.  Like in our civic calendar, we have holidays that are in particular months, it's just that we often are not in tune with when those months start and end. This need no longer be the case!  Just watch the moon and you can clearly know when the month (note the similarity between this word and the word "moon") is starting.  Each new month begins with a new moon (more about that and our months in parts of two past blog posts, here and here).  (See- it does make sense!) As the moon grows we know that we will soon find ourselves in the middle of our Hebrew month.  In fact, Passover, Sukkot, Tu b'Shevat and Purim all fall right on, or just about on, a full moon!  Hanukkah, our holiday of bringing light into darkness, surprisingly falls as the moon is waning - the 25th of the month of Kislev- and concludes on the 2nd of the month of Tevet.  This holiday then takes us from the darkest time of the year, as we approach and pass through the days when there is no moon and we are as close to the winter solstice as possible, and out the other side.  By the time Hanukkah comes to an end the light on our menorahs has increased in its fullness and the moon takes over again, increasing in her fullness. 

However, if we had a purely lunar calendar then Hanukkah would sometimes fall in the summer, and Passover, also called the "Festival of Spring" would also fall in each of the seasons, including those that are not spring!  Why does this happen?  Because lunar months are 29-30 days long, which means that over the course of a solar year we come up 11 days short.  So year after year the holidays move by 11 days.  In our civic calendar our holidays also move every year, but just by one day.  For example- what day of the week was your birthday last year?  This year it's one day later.  And next year it will move forward again.  To adjust for this we have a Leap Year, in which we add an extra day to our calendar every 4 years.  In the Hebrew calendar we have a "Leap Month," and so every number of years we add a whole month, Adar 2, to the calendar.  This year we will see this happen, so that next year's Hanukkah (you're now all prepared for this) will actually start quite late (Dec. 25, to be precise)!

Read more on how this connects to "ZMANIM" in Part 2 of this blog post.