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 Tishrei is one of the most significant months in the Jewish calendar, filled with many important holidays and spiritual opportunities. It is the seventh month of the year when counting from Nissan. Tishrei always has 30 days, and its arrival marks a time of deep reflection, repentance, and joy.
Tishrei begins with Rosh Hashana, the Jewish New Year, which falls on the first and second days of the month. Immediately following this period comes the Fast of Gedaliah on the third day, a day of mourning for the assassination of the righteous governor Gedaliah ben Achikam, whose death marked the end of Jewish autonomy after the destruction of the First Temple. On the tenth of Tishrei, Yom Kippur, the holiest day of the year, is observed with fasting, prayer, and repentance. Soon after, on the fifteenth of Tishrei, begins the week-long festival of Sukkot, when Jews dwell in sukkot (temporary booths) to remember the journey of the Israelites in the wilderness. This is followed by Shemini Atzeret on the twenty-second, a day of spiritual gathering, and Simchat Torah, celebrated in the Diaspora on the twenty-third, marking the joyous completion and restarting of the Torah reading cycle.
Each Hebrew month is associated with deeper layers of meaning in Jewish tradition. The mazal (star sign) of Tishrei is Moznayim (Libra, the scales), symbolizing judgment and balance, which aligns perfectly with the themes of Rosh Hashana and Yom Kippur. The tribe associated with Tishrei is Ephraim, representing fruitfulness and renewal, qualities reflected in the agricultural festival of Sukkot. The precious stone of the month is the agate (shoham), known for its beauty and strength. The Hebrew letter linked to Tishrei is Lamed, symbolizing learning, aspiration, and connection to higher wisdom. The limb of the month is the gallbladder, representing discernment and balance, again echoing the themes of judgment and weighing actions.
Another fascinating aspect of Tishrei is that it is considered the month in which the world was created, according to one opinion in the Talmud. This makes it a time not only of personal renewal but of cosmic renewal. The month is also unique because it is the only one with so many consecutive days of holiness and observance, combining solemnity and joy. In this way, Tishrei sets the tone for the rest of the year, guiding individuals to strive for spiritual growth, balance, and joy in their service of Hashem.