All calendars began with people recording time by using natural cycles: days, lunar cycles (months), and solar cycles (years). Ancient Egyptians followed lunar calendar for the year. New moon occurs every 29.5 days. We have twelve months because there are twelve periods from full moon to full moon in a year. Thus ancient Greek calendar had 12 months of 30 days. The lunar calculation however when summed up, did not fit the solar cycle. This was evolved gradually to have unequal 12 months. This evolved Egyptian year was almost a quarter of a day shorter than the solar year. Julius Caesar hired an ethnic Greek from Alexandria Egypt to create the 365 day calendar with an extra day every fourth year (leap year). We now follow Gregorian calendar.