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.
The Hebrew month of Sivan, חודש סיון, is the third month of the Jewish calendar counting from Nissan. It is one of the most spiritually significant months of the year because it is the month in which the Jewish people received the Torah at Har Sinai. Sivan follows the month of Iyar and precedes Tammuz, and it always contains thirty days. In the Hebrew year 5786, Sivan begins at sunset on Sunday, May 17, 2026, and ends at nightfall on Monday, June 15, 2026.
The central event of Sivan is the festival of Shavuot, celebrated on the sixth of Sivan in Israel and on the sixth and seventh of Sivan outside of Israel. Shavuot commemorates Matan Torah, the giving of the Torah at Mount Sinai, and marks the completion of the counting of the Omer that began on Pesach. Orthodox Jewish tradition teaches that the Jewish people arrived at Sinai in complete unity, described by the Torah as being “like one person with one heart.” The days leading up to Shavuot are therefore considered days of spiritual preparation and purification. Traditional customs of Shavuot include staying awake all night learning Torah, reading Megillat Ruth, decorating synagogues and homes with greenery, and eating dairy foods such as cheesecake and blintzes.
According to Sefer Yetzirah and other traditional Jewish sources, the mazal of Sivan is Te’omim, Gemini, represented by twins. Orthodox commentators explain that the twins symbolize important spiritual pairings such as the Written Torah and Oral Torah, the two Tablets of the Covenant, and the partnership between Hashem and the Jewish people. Although Judaism acknowledges mazalot, Orthodox Judaism teaches that through Torah, prayer, and mitzvot, the Jewish people are not bound by astrology.
The tribe associated with Sivan is Zevulun, according to the teachings of the Arizal and other kabbalistic works. Zevulun was known for commerce and for supporting Torah scholarship through its partnership with the tribe of Yissachar. This relationship became the classic model of supporting Torah learning.
The Hebrew letter connected to Sivan is ז (Zayin), which is associated in Jewish thought with nourishment, spiritual sustenance, and holiness. Some sources explain that because the Torah was given on Shabbat, which is sustained spiritually through the concept represented by the Zayin, the month carries a special connection to blessing and holiness.
Sefer Yetzirah also associates Sivan with the right foot and the power of movement. This reflects the spiritual journey of the Jewish people traveling toward Mount Sinai and symbolizes growth, progress, and advancement in Torah and mitzvot. The precious stone linked with Sivan is traditionally identified as Bareket, often translated as emerald, from the stones of the Choshen worn by the Kohen Gadol. The emerald’s vibrant green color symbolizes growth, clarity, blessing, and spiritual vitality.
Several meaningful dates occur during Sivan. On the first of Sivan, the Jewish people arrived at Mount Sinai. The second through fifth of Sivan are traditionally viewed as days of preparation before receiving the Torah. The sixth of Sivan is Shavuot itself, while the seventh of Sivan is observed as the second day of Yom Tov outside Israel. Throughout Jewish history, additional dates in Sivan were observed in certain communities as days of remembrance or fasting connected to historical events.
Sivan is ultimately a month of Torah, unity, and spiritual renewal. The journey from Pesach to Shavuot teaches that physical freedom alone is incomplete without spiritual purpose. During Sivan, many Jews strengthen their Torah learning, renew commitments to mitzvot, and reflect on the covenant between Hashem and the Jewish people. The month serves as a yearly reminder that the giving of the Torah was not merely a historical event, but an ongoing source of Jewish identity and spiritual life.