Roman calendar ancient Greek calendars; and the Gregorian calendar, which refined the Julian system to bring it into still closer alignment with the solar year and is the basis of the current international standard. Roman dates were counted inclusively forward to the next of three principal days: the first of the month (the kalends), a day less than the middle of the month (the ides), and eight days—nine, counting inclusively—before this (the nones). The original calendar consisted of 10 months beginning in spring with March; winter was left as an unassigned span of days. These months ran for 38 nundinal cycles, each
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