Parashat Bo continues the story of Moses and Aaron confronting Pharaoh, demanding that the King of Egypt allow the Israelites to go out into the wilderness to worship God.  As he refuses, they announce each calamity that God is about to bring upon the Egyptians.  The devastation wrought by the plagues on Egypt worsens, and Pharaoh’s stubbornness begins to show cracks.  He offers to let just the men go, but then he changes his mind.  Then he agrees that the children and the elderly can go as well, but he backtracks once again.  Finally, Moses announces that the entire nation is simply going to leave with all of their belongings.  Furthermore, Pharaoh himself will supply the cattle that will be used as offerings to God.

Moses declares the upcoming tenth plague, the death of all first born humans and animals in the land of Egypt, and then the Torah takes a break.

God speaks to Moses and Aaron, saying the following:

Hachodesh hazeh lakhem rosh chodashim, rishon hu lakhem l’chodshei hashanah

This chodesh shall be for you the head of the chodashim, it shall be first for you of the chodashim of the year.  (Exodus 12:2)

Our tradition understands this to be the first of the Torah’s 613 mitzvot.  Because of its position as number one, and because it interrupts this dramatic story, we can assume that it is telling us something highly significant.

Indeed, this verse is the origin of the Hebrew calendar.  The Rabbis do some very close reading to explain how the Hebrew calendar, which came into existence long before they came along, is rooted in the Torah.

Moses and Aaron are told that this chodesh will serve as the first chodesh of the year.  But what is a chodesh?

Chodesh is from the same root as chadash, meaning new.  The chodesh is something that is mitchadesh, that experiences renewal.

The appearance of the moon changes from one day to the next, such that it renews itself once per month.  The sun, on the other hand, appears the same each day.  Thus, the Rabbis of the Talmud (BT Megillah 5a) explain that we count the year by months, rather than by days.  The term chodshei hashanah, the months of the year, illustrate this requirement.  This is why our calendar is a lunar calendar, rather than a solar calendar.

But this leads to several problems.

A lunar month is 29 days, 12 hours, 44 minutes, and 2.976 seconds, approximately.  Twelve months is 354 days and a fraction.  This would make a lunar year about 11 days shorter than a solar year.  If we were to follow just a lunar system, the months, and the Jewish holidays, would float across the seasons, taking about 33 years to return full-circle to the season in which they started.  That is, in fact, how the Muslim calendar works.

Deuteronomy states shamor et chodesh ha-Aviv v’asita Pesach.  “Observe the month of Aviv and offer a passover sacrifice to the Lord your God, for it was in the month of Aviv, at night, that the Lord your God freed you from Egypt.”  (Deuteronomy 16:1).  Aviv is the only named month in the Torah.  It literally means “new ears of grain” because it is the month in which the ears of grain first appear.  If the calendar were to float over the course of the seasons, then we would not be observing Passover during Aviv.

Furthermore, with regard to Succot, the Torah says b’asaf’cha et ma’asecha min hasadeh – “when you bring in your produce from the field.”  This means that Succot must always take place at the time of the fall harvest.  Therefore, the Rabbis of the Talmud explain, we have to occasionally make an adjustment by adding a thirteenth month.  (BT Rosh Hashanah 7a)  In this way, we will be able to celebrate Passover and Succot in the appropriate seasons.

In ancient times, the adjustments would be made based on the observance of spring-like changes.  If the trees had not yet begun to blossom or barley had not yet started ripening, then the Sanhedrin, the ancient Jewish court that met in the Temple, would delay the beginning of the year by adding a thirteenth month.  The additional month, following Adar, we now refer to as Adar Bet.

Now that we have a fixed calendar, the addition of the extra month happens on a predetermined schedule, seven times out of every nineteen years.

But there is another problem.  When is the Jewish new year?

In the Mishnah, we read that there are actually four, or maybe even five new years, each marking something different.  Nisan is the New Year for counting holidays and for kings.  Tishrei is the new year for counting years, sabbatical and jubilee years, and for several other agricultural purposes. (Mishnah Rosh Hashanah 1:1)

The Talmud records an argument between two rabbis about when the creation of the world occurred.  One Rabbi says that it happened in Nisan.  The other says it happened in Tishrei.  So we seem to have some ambiguity.

In the Torah, the new year occurs on the first day of the month we know as Nisan.  This is the same month as the month of Aviv I just mentioned.  The Torah, indeed most of the Bible, does not have names for any of the months.  Instead, it references the month number, always referring back to the month in which the Israelites went out of Egypt.

For example, what we refer to as Rosh Hashanah, occurring on the first of Tishrei, is instead name Yom Teruah, a Day of Blasting, and takes place on the first day of the seventh month.  When the Israelites get to Mount Sinai and camp out around the base, preparing to receive the Ten Commandments, the Torah states:

On the third new moon after the Israelites had gone forth from the land of Egypt, on that very day, they entered the wilderness of Sinai.  (Exodus 19:1)

The Book of Numbers begins as follows:

On the first day of the second month, in the second year following the exodus from the land of Egypt, the Lord spoke to Moses in the wilderness of Sinai…  (Number 1:1)

Centuries later, the Bible continues to look back to this moment.

In the four hundred and eightieth year after the Israelites left the land of Egypt, in the month of Ziv―that is, the second month―in the fourth year of his reign over Israel, Solomon began to build the House of the Lord.  (I Kings 6:1)

Throughout the Bible, whenever dates are referenced, it is by a number counting back to the first of Nisan in the year in which the Israelites left Egypt.

What we know as the Hebrew months (Tishrei, Cheshvan, Kislev, Tevet…) do not appear until later books of the Bible, such as Esther.  In fact, the “Hebrew months” are in fact Persian names which were assimilated into the Jewish calendar at some point late in the Biblical era.

Why is all of this important?  Couldn’t the Israelites haves simply taken the Egyptian calendar with them, or adopted the Canaanite calendar?  Why did our ancient ancestors need to have a different calendar?  Why is it important for us to continue to keep a different calendar?

How we measure time is extremely important.  Having a Jewish calendar, and marking our years according to it, distinguishes us, especially when we are living in a society that counts time differently.

The twelfth century Torah commentator Rashbam explains that the calendar is oriented in this way so that we always have the Exodus from Egypt in our consciousness.  The Exodus is the formative moment of the Jewish people.  Its memory is supposed to have a profound effect on our lives, both individually and collectively.

As we read in the Haggadah for Passover, we are instructed to recall the Exodus all the days of our lives, and even the nights.  We mention it in our daily prayers.  We connect it to Shabbat by calling it zekher liztziat mitzrayim, a remembrance of the Exodus from Egypt, when we recite Kiddush.  And, our calendar itself also reminds us of that formative event.

Nachmanides points out that when the Torah states “this month shall be for you…” it puts things into a relative context that is particular to the Jewish people.  While Tishrei might be the universal month of creation, and the month from which we count the earth itself, we are also to think of time in its relationship to our particular story.  Our story began when our ancestors first became free.

Being conscious of Jewish time offers great meaning for our lives.  We count our week from Yom Rishon, the first day, up to Yom Shishi, the sixth day, keeping ourselves oriented towards the day of rest throughout the week.  We mark our months by the waxing and waning of the moon, and experience renewal every 29 or 30 days.  We remember our exodus from Egypt, and express our gratitude for freedom by caring for those who are suffering.  And we mark the yearly birthday of the world, marveling at the miracle of Creation and committing ourselves to do better and be more.

That is what it means to live in Jewish time.