Chinese calendar by mountain peoples. After Qin Shi Huang unified China under the Qin dynasty in 221 BC, the Qin calendar () was introduced. It followed most of the rules governing the Zhuanxu calendar, but the month order was that of the Xia calendar; the year began with month 10 and ended with month 9, analogous to a Gregorian calendar beginning in October and ending in September. The intercalary month, known as the second "Jiǔyuè" (), was placed at the end of the year. The Qin calendar was used into the Han dynasty. Emperor Wu of Han introduced reforms halfway through his
Adoption of the Gregorian calendar No. 28 of Month 1 () On the other hand, people never call dates on the Chinese calendar as "No. "dd".", which avoids any possible ambiguity. When referencing dates before the introduction of the Gregorian calendar in 1582, the official Chinese calendar may either inherit the issues with earlier calendars to be historically correct or follow the proleptic Gregorian calendar if so specified. The Islamic calendar is a lunar one, so that there are twelve lunar months in a year of 354 or 355 days, being 11 days shorter than a solar year. Consequently, holy days in Islam migrate around