For millennia humans have lived without a calendar as we know it. There was no way to tell one day from another, one could only observe the slow progression of the seasons. The lunar cycle has often been of great importance for providing key times for spiritual and practical activities, but the lunar cycle is at odds with the annual cycle. There is not a whole number of lunar cycles in one annual cycle.
For us in the 21st century it is hard to imagine that it hasn't always be normal to say “today is the 16th of March” or “ we will meet on October 13th ” and then knowing precisely which day you mean.
Natural “clocks” are the day and night cycle, the Moon cycle and the seasons. But especially these last, the seasons, could not be accurately defined. Nature told you a lot, but never precise. There was a need for some accurate reference points throughout the year. This was important for agriculture (readying the land, sowing, caring for the crops and harvesting and animal behaviour for hunting, etc.). There also was a need for the spiritual side, knowing when it was the right time for certain celebrations, offerings, etc.
Astronomy has provided techniques and methods for this since ancient times. In this module we will explain the astronomical background of a technique called heliacal rising to define a particular time of year, and make reference to the way the Tangata Whenua in New Zealand traditionally define and celebrate the New Year.