We’ve moved through several thousand years of history. We’ve seen calendars change from stone arrangements used to mark the solstice and predict the return of migrating animals; through the tracking of the stars and the counting of months. Mostly what we’ve seen through the metamorphous of the calendar, is various cultures and empires struggling to produce a way of counting days and months in a year. Their difficulty was taking into account the extra quarter-day that the Earth uses to get back to its starting point. Without taking that time into account, they’d see the calendar slip through the year. We’ve also seen some creative names for the months those calendars have come up with.