Some ancient calendars: The Sumerian calendar The first identified calendar was devised 5,000 years ago by the Sumerian civilisation. Little is known about this calendar which seems to have been made up of 12 months of 30 days. These 30 days were based on the lunar cycle, which actually lasted 29 1/2 days. The Babylonian calendar The Babylonian civilisation dates back to at least 4,000 BC and flourished in Asia, on the banks of the Tigris and Euphrates. Indeed, the Babylonians, Chaldaeans and Assyrians were (as far as we know) the first to observe the stars in order to divide time into months, days, hours and minutes. The Chaldaeans in particular are credited with dividing days into 12 hours, hours into 60 minutes and minutes into 60 seconds. The Chaldaeans began dividing time by lunar months, which resulted in a 360-day year. Once they realised that it did not coincide with solar time, they added 30 days every 6 years. The Egyptian calendar The Egyptian calendar stems from the Babylonian calendar. This very ancient calendar also dates back to around 3,000 BC. It is generally agreed that the Egyptian year lasted 360 days (some say it lasted 365 days) and was divided into 3 seasons of 4 months each.We are indebted to the Egyptians for dividing the day into 24 hours. The Maya calendar The Maya calendar is influenced by the Olmec calendar and probably dates back to the first century BC. This ancient Maya calendar is still used in southern Mexico and the highlands. The calendar was very accurate (some regard it as more accurate than our current calendar) but also very complex. The calendar was in fact a combination of a sacred cycle of 260 days and a vague cycle of 365 days. These two cycles coincided only once every 52 years of the Mayan year (roughly one of our centuries). The Sacred cycle of 260 days was divided into 2 interlocking time cycles of 13 and 20 days. The priests alone were able to establish the sacred calendar. The Sacred cycle was used for all activities relating to the gods. The vague year, or haab, of 365 days comprised 18 months of 20 days each and ended in a period of five days. These 5 days (uayeb) represented a period of bad luck. This calendar is a solar calendar. The 18 maya months: Pop, Uo, Zip, Zotz, Tzec, Xuc, Yaxkin, Mol, Chen, Yax, Zac, Ceh, Mac, Kankin, Maun, Pax, Kayab, Cumku, and uayeb. In addition to these 2 cycles, the Maya used another system for charting time!! The Aztec calendar The Aztec calendar consisted of 18 months of 20 days, making a total of 360 days plus five ill-fated days. It was a solar calendar. The Baha'i calendar The Baha'i calendar consists of 19 months of 19 days plus 4 or 5 intercalary days. It was a solar calendar.