As we live, we are aware of the reality of the passage of time. The sun rises and sets, and we experience a day. A simple sundial can measure the passage of a day and can be used to create sub-divisions of it. To complicate things, though, the sun's altitude in the sky decreases at higher latitudes, which produces longer shadows than at lower latitudes, so the performance of sundials is not uniform. On top of this, we know that a day is not of uniform length. For, as we regularly experience the lengthening and the shortening of days, we mark the passage of a year as measured by this basic solar experience.
The phases of the moon change the appearance of the night sky across a lunar month, and this too can be used to mark the passage of time. In this way, the lunar experience is added to the solar experience. But it works to a different cycle.
Prehistoric stone alignments (such as Avebury, Stonehenge and others in the UK and globally) appear aligned on the different positions of the sun and/or moon (for example summer sunrise, winter moonrise etc) at different times of the year. In that sense they appear to be calendrical and were almost certainly connected to seasonal ceremonies and agricultural activities.
Then there are stellar patterns, as stars appear in different parts of the sky at different times of the year. This was observed by people from the earliest times and probably used to mark seasonality and cultural events. The oldest image of a star pattern is thought to be that found carved on a piece of mammoth tusk dating from circa 30,500 BC. It is thought to show the constellation of Orion. Babylonian records of observations of heavenly events date back to circa 1,600 BC. Some prehistoric stone alignments may be connected to changing star patterns in the night sky. The Borana people of East Africa later based a complex calendar on observations of the star clusters near 'Orion's belt'.
The seasons roll on their annual course: winter, spring, summer, autumn. The last of the leaves fall, frost occurs, and we realise winter has started again. Another year has passed. Well, at least that is the seasonal cycle in the northern hemisphere. It is, of course, different in the southern hemisphere but the annual cycle can still be observed.
In other parts of the world the natural seasonal cycle is different; it may be more or less pronounced, but people are still aware of the passage of time across the year. And other natural cycles occur too. The monsoon begins and ends; and a yearly cycle passes once more as measured by its winds and rainfall. Then there are seasonal flowerings of plants and migrations of birds and animals. However, it should be noted that just how many 'seasons' a year is divided into is a human construction based on dividing up the phases of natural phenomena. Plus, we all see (and feel) human life alter over time. Babies grow. All of us age!
In short, the passage of time is hardwired into our existence and our experience. But how we measure it is a rather different matter. The units we choose are variable across history and cultures. And the differences noted in the solar and lunar cycles remind us that, even in the natural world, the passage of time is not uniformly experienced in natural phenomena.
At the start of a new year, we become increasingly aware of the marking of time into significant chunks and milestones. Yet, we frequently take for granted the milestones that are used by our own culture. A brief look at some of these will soon remind us of how variable these are and of how they are rooted in different historical experiences.
How to divide a day?
The natural cycle dictates a day. But it does not decide how we culturally demarcate its passage. In Judaism the next day starts at sundown, not in the middle of the night. So, what is the evening of 'Day A' in communities influenced by Western Christian culture (which moved away from Jewish day-divisions) is early in 'Day B' in Jewish reckoning. Consequently, it was important that Jesus be buried before nightfall on what English-speaking Christians later called a 'Friday,' because that was when the next day – Sabbath – started, on what English-speaking Christians later called, a Saturday.
The concept of a 24-hour day seems to be rooted in the Egyptian New Kingdom (1,550 to 1,070 BC), although hours were of different lengths. The Greek astronomer Hipparchus (died after 127 BC) later contributed to the 24-hour day idea, although the 13th century Islamic scholar, Abū al-Ḥasan al-Marrakushi, is often credited with introducing the idea of equal-length hours of the day.
We have noted Babylonian records of patterns in the sky. This was later built into divisions that influence common timing and calendrical divisions still used today. As the number 60 has many divisors, this seems to have led to their decision to adopt 360 days as the length of the year and it was connected to the fact that the sun moves through the sky, relative to fixed stars, at about 1 degree of movement each day. The Babylonian base-60 fraction system continues to inform divisions of degrees, hours, minutes and seconds. This was because it is easier to calculate with than the alternative fractions which were used in Ancient Egypt and Ancient Greece.
What makes a week?
Most of the world – due to the globalisation that has occurred over the past three centuries – now operates on a week lasting seven days. However, earlier cultures had different lengths of weeks. These included a 10-day week in Ancient Egypt and an eight-day week used by Etruscans in Italy. Early Romans adopted this last pattern but, by the 4th century AD, were moving to a 7-day week under Christian influence. This, of course, was based on Jewish culture. In AD 321, Emperor Constantine decreed a seven-day week in the Roman Empire. This included making Sunday a public holiday.
The seven-day week had an interesting history. We have already noted its importance in Judaism, where the creation story in Genesis pictured God creating over six days and declaring the seventh day a 'day of rest' – the Jewish Sabbath (Shabbat). This was (and is) on the day of the week before the one marked as such by Christians. It is a reminder that the resurrection of Jesus occurred on the first day of the working week in Judaism. This then became, for Christians, the 'day of rest'. This is an example of how the significance of the passage of time is culturally decided and can change over time. Islam also works on a seven-day week but with the 'day of congregation' (yaum al-jum'ah) being on a Friday.
Other ancient Middle Eastern cultures (recorded as far back as King Sargon of Akkad, in circa 2,300 BC) venerated the number seven as a time-period division.
What really constitutes a year?
We have seen how the Babylonians had a year of 360 days. The Babylonians also devised a year of 12 months, with each month made up of 30 days.
A similar, Chinese, pattern of a 12-month-year, with the occasional occurrence of a 13th month, can be dated to circa 2000 BC. However, a calendar of 366 days (based on the movements of the sun and moon) can be identified from circa 3,000 BC in China. But there was a problem. The Chinese were aware that this was not accurate and, by the 2nd century AD, realised it became unreliable over 300 years.
The problem is rooted in a phenomenon called 'precession'. This is the gradual movement of the Earth's rotational axis in a circle relative to the fixed stars. It means that the length of the year is not actually a fixed period of time. This was recognised by astronomers over 2,000 years ago.
The very early Romans (they of the eight-day week) originally had a 10-month year. That is why their names for September, October, November and December indicate that they are the 7th, 8th (think eight-armed octopus), 9th and 10th months, when they are now the 9th, 10th, 11th and 12th months in a 12-month year. Incidentally, the Romans expanded to a 12-month year as early as 713 BC but since their year started in March the old names still worked. The year lasted 355 days. However, they knew there was a problem and later, every two or three years, would deploy an extra month.
Political considerations ('Is a shorter or longer year politically useful right now?!') meant this was poorly applied. By the middle of the 1st century BC the official calendar was getting well out of sync with the reality of the seasons! To cut a long story short, Julius Caesar took on board Egyptian calculations, the result being a year of 365 days, with an extra day added to each year that was divisible by 4 (because a solar year was calculated as lasting 365 and a quarter days). This became known as the 'Julian Calendar'.
Problem sorted. Well, no. The 'Julian Calendar' assumes that a solar year lasts 365.25 days. However, it actually lasts 365.24219 days! The difference slowly causes administrative problems over time. In the 4th century AD the – newly Christianising - Empire decided that Easter Sunday would fall on the first Sunday, after the first full moon after the spring equinox (when the hours of day and night are equal). This last event was tricky to calculate, so it was decided that it would be on 21 March each year. Over time, this date fell later and later in the year, compared to what it had done back in the time of Julius Caesar. If nothing was done about this, Easter would eventually fall in the early summer (clearly at odds with its springtime setting).
In 1582, Pope Gregory XIII acted. The calendar was reset: October that year lost 10 days; after 1600 no year exactly divisible by 100 would be a leap year (except when it was divisible by 400). For those reading this and (like me) wishing they had concentrated more in maths lessons, suffice it to say that it (basically) fixed the problem! This is the 'Gregorian Calendar.
Problem finally sorted? Well, kind of! Due to it being devised by a pope, many Protestant and Eastern churches were reluctant to adopt it. It was not until 1752 that the UK finally brought its calendar into line with the Gregorian system, by taking 11 days out of September that year, and then – thereafter – following the 'Gregorian Calendar'. Others stood out longer. Russia, for example, did not change until after the 1917 Revolution. Consequently, the Bolshevik 'October Revolution,' took place on 7 November 1917 in the modern calendar! That is why some UK school history textbooks date it to that month, whereas no tractor factory in the USSR was ever named 'Red November'!
The law which changed the UK to the 'Gregorian Calendar' also decided that 1752 would start on 1 January. Before that, years were reckoned in many Western Christian nations to start on 25 March ('Lady Day,' the date decided in medieval times as the 'Feast of the Annunciation'). Until then the UK Tax Year started the day after: 26 March. In 1758, the 11-day change of 1752 was applied to it as well and moved it to 6 April. It has remained there ever since. That is why the UK Tax Year does not start on 1 January!
Synchronise watches!
Today we take accurate measurement of time for granted. And we assume uniformity of it within demarcated time zones. But these – while rooted in the reality of the movement of the earth – are still artificial constructions. We in the UK and the Republic of Ireland are members of one time zone. However, the sun does not know that. For example, before the 19th century, 'Local-Time' (originally based on local sundials) across Britain varied: 'Oxford Time' was 5 minutes behind 'Greenwich Time' (ie 'London Time'), 'Bristol Time' was 10 minutes behind, and 'Exeter Time' was 14 minutes behind it. Try running a railway on that system!
In November 1840, the Great Western Railway in England established a single standard time across its network. By 1855, 'Railway Time' (which was 'London Time') was communicated by the new telegraph system. Before that, train guards passed on the time from Paddington across the system. By 1855, 98 per cent of towns and cities in the UK had transferred to 'London Time'. But there was resistance! Public clocks in Exeter, for example, continued to show 'Local Time' and only revealed 'London Time' (14 minutes ahead) via a second hand added to the clocks! This was due to the reluctance of the Dean of Exeter Cathedral to give in to the railway companies; and so the cathedral clock resolutely showed the local time. It was not until 1880 that an act of parliament established uniform time across the whole of Britain.
As we begin this new year, spare a thought for the millennia of historical calculations that lie behind these (apparently) straightforward actions. Happy New Year!
Martyn Whittock is a historian and a Licensed Lay Minister in the Church of England. The author, or co-author, of fifty-six books, his work covers a wide range of historical and theological themes. In addition, as a commentator and columnist, he has written for several print and online news platforms and been interviewed on TV and radio news and discussion programmes exploring the interaction of faith and politics. These have included being interviewed on news platforms concerning the religious dimension to current US politics, Christianity and the Crown in the UK, and the war in Ukraine. His most recent books include: Trump and the Puritans (2020), The Secret History of Soviet Russia's Police State (2020), Daughters of Eve (2021), Jesus the Unauthorized Biography (2021), The End Times, Again? (2021), The Story of the Cross (2021), Apocalyptic Politics (2022), and American Vikings (2023).
