Final answer:
Rosh Chodesh is celebrated for two days at the beginning of each month in the Hebrew calendar, except for Tishrei where it's one day. It marks the start of a new month based on the lunar cycle, connected to ancient traditions and various cultural calendar systems like the Coptic Christian church in Ethiopia.
Step-by-step explanation:
Rosh Chodesh, which means 'head of the month,' is a minor Jewish holiday that marks the beginning of a new month in the Hebrew calendar. Traditionally, Rosh Chodesh is celebrated for two days at the beginning of each month, except for the month of Tishrei, where it is observed for only one day. This observance corresponds to the new moon, with the first sighting of the monthly lunar crescent signaling the start of a new month.
The concept of Rosh Chodesh reflects the ancient connection between lunar cycles and calendar months, a connection that is evident in the etymology of terms for 'month' in various languages such as Arabic's 'shahr' and Hebrew's 'yerach' and 'chodesh.' The latter term derives from the Hebrew word for 'new,' emphasizing that the month was once reckoned from new moon to next new moon. The history and origins of lunar-based calendars reach back to ancient civilizations, including the city of Jericho, which derived its name from 'yerach,' reflecting a deep historical link to the moon's influence over human societies.
In contrast to this lunar calendar system, the civil year associated with the Gregorian calendar (January to December) does not align its months with the lunar cycle. Instead, it is a solar calendar with fixed months. Still, the way various cultures around the world have structured their calendars over millennia continues to fascinate, such as the Ethiopian Coptic Christian church calendar that boasts 12 months of 30 days each plus an additional short 13th month.