Thursday, 17 October 2013


“I don’t wait for the calendar to figure out when I should live life.” - Gene Simmons

Time has always fascinated human beings. The intangible and yet inexorable passage of the hours, the endless procession of the seasons, the death and regenerative cycles of crops and vegetation have necessitated the use of a calendar.  The farmer has to know when to sow his plants, the priest when to glorify his gods, the king when to lead his army to battle.  And so were born calendars, to keep time and to reckon the passage of the seasons and the years.  Each culture tried to solve the problem of time keeping and calendar construction in its own way and vestiges of these multiple calendars are still to be found around the world.  Currently, there are about 40 different calendrical systems in use worldwide, with about six widely used.  The Gregorian calendar is the most widespread, and by convention, used in most (if not all) secular activities around the world. This calendar is solar one and it is based on the ancient Roman calendar as modified by Pope Gregory XIII (7 January 1502 – 10 April 1585).

The solar year depends on the revolution of the Earth around the sun, each revolution taking 365.2422 days.  The tilt of the Earth’s axis is responsible for the seasons. At the same time, the moon has influenced the development of a calendar with each lunar cycle lasting for approximately 1/12 of the solar year. This has given rise to subdivision of the year into 12, sometimes 13 months.  The word month itself shows its close association with the word moon.  The ancient Greeks had a similar association: mén = “month”, méne = “moon”.

The Western calendar developed from the ancient Greek and Roman calendars.  The term calendar itself is derived from the Latin calenda meaning the first day of the month.  The ancient Roman calendar is the one that corresponds most closely to our own and was called the Julian Calendar as it was standardised by Julius Caesar in 46 BC. His Greek astronomer Sosigenes devised a 12-month calendar of 365 days, with a leap year of 366 days every four years. Each month had 30 or 31 days except for February, which was considered unlucky and hence had 29 days except every leap year when it had 30.  This was until Augustus Caesar renamed the old Roman month Sextilus after himself, in the process robbing February of a day in order to increase August’s 30 days to 31.

The Julian calendar assumed that the year lasted for exactly 365.24 days.  The real year was about 11 minutes and 14 seconds shorter than the Julian year and over the decades, the seconds and minutes added up to hours and days, making the real seasons drift away from the calendrical seasons.  After a few centuries, the Church began to find it difficult to set the moveable Church feasts such as Easter, which depend on the Vernal equinox.

Pope Gregory XIII in 1582 decided to remedy the situation, which by that time had led to a calendrical discrepancy a few days ahead of the seasonal calendar.  The Pope decreed that February would have 29 days in century years that could be divided evenly by 400 (e.g. 1600, 2000), but only 28 days in century years that could not be divided evenly by 400 (e.g. 1700, 1800, 1900).  Commencing in October 1582, ten days were dropped from the calendar in order to correct the discrepancy. The resulting calendar is the Western Gregorian Calendar in use throughout most countries around the world today.

Most Catholic countries adopted the Gregorian calendrical reformations immediately after Pope Gregory’s modifications, and other Western nations followed suit soon after (e.g. France, Spain, Portugal, Luxembourg 1582).  As the Pope had no authority over the Eastern Orthodox Churches, the Julian calendar persisted in its use in the countries where the Orthodox faith was the official state religion (e.g. Russia [adopting the Gregorian calendar in 1918], Rumania [1919], Bulgaria [1915], Greece [1923]).

Even when for practical reasons the Gregorian calendar was adopted by the laity, the religious feast days continued to be calculated according to the Julian Calendar.  This situation persists in some countries to this day.  Some of the Eastern Churches calculate all of their feast days according to the Julian Calendar (which is now 13 days behind the Gregorian calendar!).  For example, the Ukrainian Orthodox Christmas is celebrated on the 7th of January.

Some other Orthodox Churches have adopted a more illogical practice.  They have embraced the Gregorian calendar for all “fixed festivals” (e.g. Christmas and the commemorative Feast Days of Saints) that recur on the same date every year.  However, when it comes to calculating the “moveable festivals” (e.g. Easter and all of the associated feasts such as Ash Wednesday, Ascension, Pentecost, etc), such Orthodox Churches use the Julian Calendar.  This leads to the curious situation of the Greek Orthodox and Catholic devotees celebrating Christmas together on the same date and Easter at different times.

Easter is an interesting example as the Paschal dates are calculated on the seasonal calendar, re-enforcing the fact that Easter is an old Spring fertility festival (Eostra was the name of the Celtic Spring goddess).  Easter is celebrated on the first Sunday after the first full moon following the Spring Equinox on the 21st of March.  The dates of all other moveable feasts are calculated in connection with the date set for Easter in that year.  If there is no full moon between the Spring equinox calculated according to the Gregorian calendar and the Spring Equinox according to the Julian calendar, then Catholic and Orthodox Easter occur at the same time.  This happened in 1977, 1987, 1991, and will periodically recur until reason prevails and the Gregorian calendar is adopted universally.  An even more logical approach would be to specify Easter as always being celebrated on the third Sunday in April, for example. What a boon for time-tablers, schedulers and forward planners that would be!


  1. An interesting post ... I have always been confused by these two different calendars ... it makes sense now (or until some time has passed and I try to make sense of them again!) ... Is that first photo the astronomical clock in Prague?

  2. Fascinating! I had no idea it was all so convoluted...

  3. Amazing how long it took some countries to adopt the Gregorian calendar! I had to laugh about the logical Easter dates! It maybe will happen in two hundred years...