What is Time, lunar and solar calendars

What is Time? Lunar vs Solar Calendar

The significant differences in the length of the solar and lunar years, and the reliance on both the sun and the moon to determine the daily routines of our lives highlights basic paradoxes that have to be controlled by a central calendar-making authority.

The development of our record of everyday time, as expressed through the use of calendars, is a vivid story of tension and conflict: between religious institutions and political authorities, between factions within faiths and, fundamentally, between the different lengths of the solar year and the lunar year.

Western Christian faiths valued the date of Easter above all others. As most cultures were strictly ruled either by or alongside a religious authority, the dates of worship were more than a simple matter of noting time. Like the sculpting of the hidden gargoyles of Canterbury Cathedral (the actual making of which was the act worship), or the rituals of Shabbat to the Jewish religion, certain actions are an article of faith in their own right, whether observed publicly or in private: a fundamental expression of a whole way of life.

The Effect on Daily Life

time, calendar, old calendar,For most people, up to the end of the Middle Ages, life was lonely, dirty and extremely hard work. The rhythm of the seasons and the ending and arrival of daylight were pillars of their short lives (people lived on average no longer than 35 years).

Unfortunately, these two rhythms – the season and the day – work against each other, because the 12 lunar months of 29 and a half days produce a shorter year than the measurement from one year to the next of the date of the spring and autumn equinoxes (when the sun crosses the equator and day and night are of equal length everywhere on earth, generally around 21 March and 23 September) and the summer and winter solstices (22 June and 22 December). The lunar year, at 354 days, is just over 11 days short of the solar year.

A further complication is that, because the earth does not rotate around the sun in a perfect circle, there is some shifting between one year and the next for these equinoxes and solstices.

Global Considerations

Time, calendar, astrology, old calendarPractical problems only manifest themselves over many years – for example, the Julian calendar became a concern for the Christian faith, which placed high authority on the date of the risen Christ at Easter, only to realise that the date had moved backwards. By the time of the Gregorian calendar reform in the sixteenth century, Easter was 11 days nearer summer, a long way from the spring equinox. In AD 325 the Council of Nicea had agreed that Easter should be on the first Sunday after the first full moon after the vernal equinox, making it between 23 March and 25 April. Over the centuries there have been many attempts to fix Easter, like Christmas, to a particular date, one of the most recent of which was a move in 1923 by the then League of Nations. But agreement was never reached.

A further practical issue is the need to establish a reliable system between cultures which trade or war with each other (both of which have been features of humankind’s relationship with itself over the millennia).  The calendar used in Iraqi and Aphganistan is slightly different to the one generally accepted in Europe and the USA, a fact not understood by the military hierarchy, causing terrible human suffering during times of religious observance in the wars of the last decades.

Mean starting date for each Season

A short reminder to finish off:

  • Vernal Equinox has equal hours, day and night 21 March
  • Summer Solstice is longest day of the year 22 June
  • Autumn Equinox has equal hours, day and night 23 September
  • Winter Solstice is shortest day of the year 22 December

The next What is Time? article will cover ancient calendars, from Egyptian and Mesopotamian to early Roman.

Some other posts of interest.

The image in the head of this post is an illustration of the Copernican system of the universe, from The Harmonia Macrocosmica of Andreas Cellarius (published in 1660)