Calendars: The business world generally runs on the western secular year, beginning with January 1 and ending with December 31. However, many cultures use other calendars to determine holidays such as New Years or specific holy days. For example, Eastern Orthodox Christians celebrate Christmas on a different day from western Christians. For Muslims, Friday is a day for prayer. Jews observe holidays ranging from Rosh Hashanah to Yom Kippur. These variations affect the workplace as people require time off to observe their holidays.