How booking the right day became an art

Ancient China had the world's most-developed calendrical system, since agriculture was closely related with the seasons and launching new calendars for the coming year was an important symbol of a new emperor's rein, Zhang Peiyu, a scholar who studies the history of astronomy, writes in Chinese Ancient Calendars, published in 2008.

"An emperor's reign was accepted only when the subjects used his calendar," he writes.

"So, all the rulers for more than 3,500 years, starting with the Shang Dynasty (c. 16th century-11th century BC) and running through the Qing Dynasty (1644-1911), followed this idea. This made China the country with the world's most-advanced calendar system.