Rosh Chodesh

For most of the Second Temple period, the start of a new Jewish month was determined by direct observation: witnesses who saw the first sliver of the new moon reported their sighting to the rabbinic court in Jerusalem, which examined them and, if satisfied, formally sanctified the new month and sent word by messenger and signal fire to communities elsewhere. Because the exact day depended on witness testimony and could not always be predicted in advance, communities at a distance from Jerusalem, uncertain whether a month had been declared on its earliest or latest possible day, developed the practice of observing two days at the start of some months and, eventually, two days for each of the major festivals as well, a practice that survives outside the land of Israel to this day even though its original cause no longer applies.

The system of direct observation broke down as the rabbinic center in the land of Israel came under increasing political pressure, and by the middle of the fourth century CE a fixed mathematical calendar, attributed by later tradition to the patriarch Hillel II, replaced witness testimony with a calculated cycle that could be projected indefinitely into the future without requiring a functioning court in the land of Israel at all.

The Babylonian Talmud records a tradition that women are exempted from certain categories of labor on Rosh Chodesh, and links the exemption to a story in which the women of the wilderness generation refused to surrender their jewelry to be melted down for the golden calf, receiving the new moon festival as a reward for their faithfulness where the men who had contributed their gold did not. The custom of women refraining from sewing, weaving, or similar work on the day is attested in later halakhic literature across a range of communities, though its observance had become uneven and, in many places, largely forgotten by the twentieth century.

From the 1970s onward, women within various streams of American Judaism revived and reinterpreted Rosh Chodesh as an occasion of their own, forming Rosh Chodesh groups that meet monthly for study, ritual and discussion tied loosely or closely to the new moon and to the day's older association with women. The contemporary movement draws explicitly on the Talmudic precedent while building new liturgy and practice largely absent from the historical record, a combination its own participants generally describe as renewal rather than as strict restoration of a single earlier practice.