When you think of the really significant shabbatot throughout the Jewish calendar, you think of Shabbat Ha-Gadol, Shabbat Shuva, and the singles among us think of shabbat nachamu.  But, in actuality this shabbat perhaps is the most significant shabbat in our calendar, and it truly represents our destiny as Jews.  This shabbat is shabbat-rosh chodesh; a shabbat that coincides with the beginning of our month.

What we should understand about shabbat-rosh chodesh is that it's not just another day in the Jewish year; its not a day that we should just gloss over.  In fact, it is a special and holy day--that should inspire us to reevaluate our lives.  Let me explain.
 Shabbat and Rosh Chodesh actually represent two entirely different ways of measuring time in this world.  Rosh Chodesh is based upon the lunar calendar.  Based upon the cycles of the moon, we declare our monthly calendar.  On the other hand, Shabbat is actually based upon the solar calendar.  Shabbat comes every seven days.  And a day is calculated by the complete cycle of a sun setting rising and setting.  So shabbat actually occurs on the seventh cycle of the sun setting, rising, and setting.

So today is shabbat-rosh chodesh, the unique intersection of time when we bring both those moments and cycles together.
 But in order to really understand what is so significant about shabbat-rosh chodesh, we have to understand just a little more about our calendar.   The Jewish calendar is a luni-solar calendar, which means it is based not only upon the cycles of the moon, but also upon the cycles of the sun.  We base our months upon the moon, but we base our holidays upon the sun.  We say that the holiday of Pesach must come out in the Spring, and Sukkot in the fall.   This means that these holidays are dependent upon the solar calendar, because they are dependent upon the seasons, and the four seasons are entirely dependent upon the moon.

So you see, Judaism teaches that we should have a luni-solar calendar.  The question is why do we need a calendar that is based upon both the sun and the moon?  After all, the Christain calendar--the Gregorian calendar that we use today in America--is entirely dependent upon the sun.  Our American months have nothing to do with the cycle of the moon--the whole calendar revolves around the sun.  On the other hand, the Islamic calendar has nothing to do with the sun, and is only dependent upon the moon.  That's why the Ramadan, is always moving irrespective of season--its because the Islamic system is only dependent upon the moon.

So why is it that Judaism depends not on the sun or the moon alone, but on both the sun and the moon?  This exact question was put to Rabbi Shimon b. Tzemach Duran, known as the Tashbetz, who lived in North Africa in the 15th century.  R. Shimon was asked, why is it that Judaism must continually make leap years in order to have its monthly lunar calendar coincide with its yearly solar calendar…why can't Judaism just have one calendar--either a lunar system or a solar system.

So R. Shimon responded that Judaism's calendar is actually the best type of system because, unlike Christianity and Islam, it is able to utilize the advantages of both the solar and lunar calendar.  The problem with having only a solar calendar, is that the months are arbitrarily made up by man.  They have nothing to do with the cycle of the moon, man alone decides if the month will be 30 or 31 or 28 days.  In a solar calendar, the months are in effect divorced from nature.  They are solely manmade and not intrinsically connected to the world.

In a lunar calendar, however, the months are connected to nature.  Yet, a system that is entirely dependent upon a lunar calendar is also a problematic.  Look at the Islamic calendar, the holiday of Ramadan does not always come out in the same season, but rather moves throughout the year.  It’s a calendar that is too transient.  There is no permanence and no connection between the holidays and the seasons.

So according to R. Shimon what Judaism does as a result is combine the two calendars.  In doing so, we balance the fact that we are always connected to nature through the cycles of the moon, and yet at the same time we are not entirely dependent upon the whims of nature.  By anchoring the calendar to the solar system, we have also established some permanence to our calendar.

Classically, our commentators see in this luni-solar system the meeting of God and man in one calendar.  God determines the season, but yet he allows man based upon nature to set the exact dates.  In this way the destiny of both God and man meet in one calendar.

Allow me to offer an alternative explanation to the symbolism of having a calendar that is based upon both a lunar and a solar system.  I think our luni-solar calendar is a system that is set up to ensure that we use time properly and measure ourselves in an effective manner.

How do we measure time?  Today we use a watch, to measure hours, and a calendar to measure days and months.  But in ancient days there were two basic ways to measure time--one was with the moon and one was with the sun.  Its easy to measure time in the short term with the moon--you can easily see changes in the size of the moon.  In a relatively short period of time, the moon goes from nothing to being full and back to nothing again.  So the moon is excellent as a short term measurement.  But in the long term it has shortcomings.  In order to measure properly in the long term we need to use a more fixed object like the sun.  The sun allows four basic measurements throughout the year, dependent upon the four seasons.  So the sun is very good as a system of measurement, but only in the long term.

So what Judaism teaches us is that we need to use both a lunar and a solar system as a means of measuring time.  Both are equally important.  The lunar system allows us to measure ourselves on a daily and weekly short term basis.  It allows us to mark our change daily, based upon the dynamics and hectic changes of a day to day existence.

But at the same time that we need to measure ourselves daily, Judaism also teaches us that we need to measure ourselves not just in the short term but also in the long term.  This is where the solar system of measurement comes in. The sun, with its dominating pervasiveness reminds us not to be too caught up in short term failures or successes, but also to measure ourselves over the long term--so the solaar system  teaches us to use the four seasons as four distinct measuring points through the year.
 Now, I can understand why its important to constantly measure ourselves in the short term--if you don't look at something up close you often miss the nuances and the fine points.  But why is it important to measure ourselves with such a long term system as well?  I thin one of the greatest frustrations people have in life is that they go through their day to day grinding and grueling existence, and they don’t clearly see the benefit of it.  People often ask themselves, what's it all worth.  That's why its important to look at things also with a very broad term perspective.  Look back after five or six months and see what you accomplished in your job.  See what you accomplished in your family or personal growth.

So with this luni-solar system Judaism is teaching us that when it coems to measuring in life we need to utilize both this short term dynamic system, and this long term more static system.  If your'e only focusing on the short term, you will lose persepcetive, and if you only focus on the long term then you forgot about the necessity to focus every day of you life.  The luni-solar system says both are important--both the long term measuring as well as the short term.

So what's the highest point of measuring?  What's the highlight of the calendar?  That is when you actually fulfill this creed and live a day following both of these calendrical systems.  Such a day is on shabbat-rosh chodesh.  It’s a day that follows both the solar and the lunar calendars.  And consequently it’s a day that should remind us about the importance of measuring ourselves both in the long term as well as in the short term.

Just before I end, I would like to share with you one halakhah.  The Talmud (Sanhedrin, 70) teaches that when they used to eat the special seudah, meal, that would be eaten on rosh chodesh, it would be eaten in a time of day that was lo yom ve-lo leila, neither day nor night.  And our commentators explain that the meal would be eaten between dawn and sunrise.

To me the importance of this halakhah is now perfectly clear.  Why was the meal celebrating the rosh chodesh eaten between night and day? --To remind us that we should not focus too heavily on either the lunar or the solar calendar.  That is, it reminds us that when we measure ourselves, both our successes and our failures, we should be careful to think both in the long term and in the short term.  Focus on the present, but always remember to take stock of our long term goals.