some findings constituted as a lunar calendar. Most related findings and materials from the palaeolithic era are fashioned from bones and stone, with various markings from tools. These markings are thought to not have been the result of marks to represent the lunar cycles but non-notational and irregular engravings, a pattern of latter subsidiary marks that disregard the previous design is indicative of the markings being the use of motifs and ritual marking instead. However, as humans' focus turned to farming the importance and reliance on understanding the rhythms and cycle of the seasons grew, and the unreliability of lunar phases became problematic. An early human accustomed to the phases of the moon would use them as a rule of thumb, and the potential for weather to interfere with reading the cycle further degraded the reliability. The length of a moon is on average less than our current month, not acting as a dependable alternate, so as years progress the room of error between would grow until some other indicator would give indication. The Ancient Egyptian calendars were some of the first calendars made, and the civil calendar even endured for a long period afterwards, surviving past even its culture's collapse and through the early Christian era. It has been assumed to have been invented near 4231 B.C. by some, but accurate and exact dating is difficult in its era and the invention has been attributed to 3200 B.C., when the first historical king of Egypt, Menes, united the Two Lands. It was originally based on cycles and phases of the moon, however, Egyptians later realised the calendar was flawed upon noticing the star Sothis rose before sunrise every 365 days, a year as we know it now, and was remade to consist of twelve months of thirty days, with five epagomenal days. The former is referred to as the Ancient Egyptians' lunar calendar, and the latter the civil calendar. Early calendars often hold an element of their respective culture's traditions and values, for example, the five day intercalary month of the Ancient Egyptian's civil calendar representing the birthdays of the gods Horus, Isis, Set, Osiris and Nephthys. The Mayans' use of a zero date as well as the Tzolkin's connection to their thirteen layers of heaven (the product of it and all the human digits, twenty, making the 260-day year of the year) and the length of time between