A calendar reflects the rhythmic course of life, at the same time guaranteeing the continuation of the rhythm. The concept of time can develop in people only on the basis of their collective experience. The events in a person's own life are insufficient for him or her to develop an awareness of time, contact with other people is also necessary. It is evident that the system of chronology must have developed somewhat differently for those tilling the land and for those engaged in hunting and fishing, since the nature of their common activities was different.
Having cultivated land since time immemorial, Estonians had probably based their system of chronology on the annual agrarian cycle long before the Christian calendar reached them. The word "aasta", the Estonian for "year", is a derivative from the words "ajast aega", which evidently means "from a certain period of time up to the same period of time". Like most European peoples, Estonians had divided the year into two parts on the basis of the annual natural cycle: the warm summertime suitable for working in the fields and grazing cattle in the pastures, and the cold wintertime, when fields were frozen and cattle had to be kept in sheds. The spring and the autumn were only like bridges for transition from one season to the other, from winter to summer and from summer to winter. In recent centuries Estonian summers began on St. George's Day (the 23rd of April) and ended on Michaelmas Day (the 29th of September).
Today the majority of the world's nations recognize the twelve months of the calendar originating from Ancient Rome and even use the same names. At the same time popular names of months, mostly based on natural phenomena and certain important days, have also been used in Estonia. Thus, for instance, April is also called St. George's month or sap month, May is also known as leafing month, green birch-bough month or flower month, etc. The names of the calendar months were probably not taken into popular use until the first Estonian language calendars were printed. The earlier system of chronology had been on the lunar calendar. Time was counted from the appearance of a new moon up to the next new moon (the length of such a month is 29.5 days). Popular religion pays great attention to the Moon. The seeming waxing and waning of the Moon had given rise to a general belief that the period of a new moon is a mild time favouring all forms of growth, while the period of an old moon is a hard time unfavourable for growth. During the period of a new moon it was advisable to shear sheep, cut hair (then wool and hair would grow again fast), slaughter animals (the meat would distend in cooking) - in a word, to do everything that was expected to succeed. The period of an old moon, on the other hand, was good for cutting down undergrowth (it would not throw out sprouts again), cleaning rooms (they would not get dirty again so soon), etc. - in a word, it was a period favouring disappearance and destruction.
More often than months the units used for counting time were weeks, from one definite day to the next:
Several of those definite days have been used to mark the starting point for counting the weeks and the yearly cycle. Most frequently the starting points were Candlemas Day (the 2nd of February), Christmas and Michaelmas (the 29th of September). In late spring, in addition to that periodisation, Estonians also used to count sowing weeks. These were counted backwards from the times of sowing. They usually ended at Midsummer Day, but in a small area in Southern Estonia also with St. James's Day (the 25th of July). From that date ten weeks (in Võru district 13 weeks) were counted backwards. Thus, the starting point was the ploughing day (the 14th of April). Sowing was started with oats in the tenth week, followed by barley, potatoes, and summer wheat, flax was sown later. The sixth sowing week (in Võru district the tenth week) was the grass week; it was believed that a field sown under grain at that time would be overgrown with weeds. The sowing weeks ended with the sowing of turnips and cabbages before Midsummer Day.
The last subdivision in the system of chronology was the day (a period of 24 hours). By the 17th century at the latest, Estonians had become familiar with the sundial and the division of a day into hours. In everyday life on farms, however, that was of no practical importance and a more general division of the day was more expedient. Also, in winter and in summer daytime was divided differently. In general, in the 19th century Estonians had two substantial meals a day in winter and three in summer. It was the meals that divided the day into parts. "Söömavahe" (the time between two meals) used to be current as a generally acceptable unit of time; for example: "it will take the time between three meals to mow this field". The proper time for the meals was determined by the sun. Following the course of the sun enabled people to divide their day much more flexibly. A written record of the Estonians' division of the day dating from the beginning of the 18th century contains 20 subdivisions. However, it was not until last century that the earlier subdivision of the day based on the light and dark time and the meals was replaced by the notion of "hour".
Essential influence on the Estonian traditional system of chronology was exerted by the Catholic Church. First and foremost, that concerned fixing the dates of definite days in the Estonian popular calendar and giving them names. The decisive factor here was their compatibility with the local economic rhythm. In the course of time only those days retained their importance that were connected with a larger number of rituals or games.