The Chinese almanac is not simply a book of auspicious days. For most of imperial history the issuing of the calendar was a sovereign act, reserved to the throne, and its distribution through the empire was one of the ways a dynasty asserted that it held the mandate. Producing an unauthorised calendar was accordingly a serious offence, punished severely under several dynasties.
That gave the astronomical bureau responsible for computing it an unusual standing, and it explains an episode that would otherwise be baffling. From the seventeenth century Jesuit missionaries were appointed to direct the imperial astronomical bureau, because their calculations of eclipses proved more accurate than those of their rivals, and a dynasty whose legitimacy rested partly on getting the calendar right had a practical reason to employ them. The arrangement lasted well over a century and produced its own controversies, including a case in which the Jesuit director was condemned to death before being reprieved.
The almanac itself combines several layers: the astronomical calendar, the sexagenary cycle of days and years, the twenty-four solar terms that govern agriculture, and the selection of days suitable or unsuitable for particular undertakings.
It survives as a living publication. Almanacs are printed annually in Hong Kong, Taiwan and among Chinese communities elsewhere, consulted for weddings, funerals, moving house and opening a business, and they remain among the best selling books of their kind.