Rosh Chodesh which literally means "Head of the Month" is a monthly holiday that celebrates the arrival of the new moon, marking the start of a new month in the Jewish calendar.
The Jewish Calendar is a lunar calendar with twelve lunar months and 354 days per year. Each lunar month consists of 29 1/2 days. Since it is impossible to switch months in the middle of the day, certain Hebrew months have twenty-nine days whilst others have thirty days.
In order for the Jewish Festivals to be synchronized with the proper season, for example Passover (Pesach) which must fall in the spring (in Israel - the Northern Hemisphere), a leap year is added every few years. In a nineteen year cycle there will be seven leap years.
The Jewish leap year, however, is not like the leap year in the Gregorian calendar which is one day added on at the end of February every four years. A Jewish leap year adds on an entire month to close the gap between the 354 day lunar calendar and the 365 day solar calendar. Since the month of Adar (approximately February-March) is the last month of the Hebrew year, we add on an extra month at this time. We then have Adar I and Adar II which assures us that the holidays will be celebrated in the proper season. Originally, the date of Rosh Chodesh was confirmed on the testimony of witnesses observing the new moon, a procedure known as Kiddush Hachodesh (sanctification of the month). After the Sanhedrin (an assembly of either 23 or 71 elders or rabbi's, appointed to sit as a tribunal in every city in ancient Israel) declared Rosh Chodesh for either a full 30 day month or a 29 day month, news of it would then be communicated throughout Israel and the diaspora.
This system was dependent on the functioning of the Sanhedrin to declare the month, and to communicate this month to far-flung Jewish communities. In the 4th century CE, this became impossible and instead a fixed calendar of 29 and 30 day months was instituted by Hillel.
At the end of a 29 day month, Rosh Chodesh is celebrated for one day, on the first day of the new month. At the end of a 30 day month, Rosh Chodesh is celebrated for two days - the 30th day of the previous month, and the 1st day of the new month.
With the exception of the month of Heshvan, the eighth month of the year, every single month of the Jewish Calendar has some sort of special day or special observance. The importance of Rosh Chodesh is therefore obvious.
The names of the months are not Hebrew but Babylonian. The Bible refers to the Jewish holidays only by the order of the months and not by the Babylonian names which were assigned long after the canonization of the Torah. For example, the Torah gives the date of Yom Kippur as the tenth day of the seventh month, whilst the date of Pesach is the fifteenth day of the first month.
Chodesh Sivan is the third month of the Jewish calendar, following Nisan and Iyar, and contains 30 days.
It holds profound spiritual and historical importance in Jewish tradition, as it is the month in which the Jewish people received the Torah at Mount Sinai. The central event of the month is the festival of Shavuot, celebrated on the 6th of Sivan, marking the giving of the Torah. Shavuot is unique among the major holidays because it is not tied to a specific agricultural milestone, but to a spiritual one—the covenant between God and Israel through the Torah.
The mazal (zodiac sign) of Sivan is Teumim (Twins). This reflects the duality and unity found in relationships such as Moses and Aaron or the Jewish people and the Torah. The symbol of twins also hints at the harmony and cooperation required to receive the Torah as one united nation.
According to the mystical tradition, each Hebrew month is associated with one of the twelve tribes of Israel. Sivan corresponds to the tribe of Zebulun, who was known for his partnership with the tribe of Issachar. While Issachar studied Torah, Zebulun supported him financially through trade. This model represents the deep interdependence between those who learn Torah and those who support its study, a theme central to Sivan.
Each month also corresponds to a specific body part, and Sivan is connected to the left foot, symbolizing forward movement and the ability to progress spiritually. Just as the left foot propels a person forward physically, Sivan invites us to take meaningful steps in our relationship with the Torah.
The Hebrew letter associated with Sivan is Zayin, which can symbolize both sustenance and spiritual strength. The letter’s shape resembles a sword, indicating the power and protection that Torah provides, but it also alludes to nourishment, as the Torah is the essential sustenance for the Jewish soul.
In terms of its connection to the Choshen Mishpat, the High Priest’s breastplate, Sivan is linked with the stone Yahalom, often identified as a clear gem such as a diamond or crystal quartz. This stone represents clarity and purity—qualities that mirror the clarity of Divine truth revealed at Sinai. The brilliance of the Yahalom reminds us of the light and wisdom contained within the Torah.