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
Celtic calendar made up of bronze fragments, in a single huge plate. It is inscribed in Gaulish with Latin characters and uses Roman numerals. The Coligny Calendar is an attempt to reconcile the cycles of the moon and sun, as is the modern Gregorian calendar. However, the Coligny calendar considers the phases of the moon to be important, and each month always begins with the same moon phase. The calendar uses a mathematical arrangement to keep a normal 12-month calendar in sync with the moon and keeps the whole system in sync by adding an intercalary month every 2 years. The Coligny