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The Calendar A Presentation by Alex Milne 7 July 2010 Meeting of the Probus Club Manotick, Ontario

Why do we have the rhyme:

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“Thirty days hath September, April, June, and November; All the rest have thirty-one, Save February, with twenty-eight days clear, And twenty-nine each leap year?”

I plan to cover these oddities and show you how they came about.

The Need for Calendars Try to place yourself back into a time when the understanding of time and the tracking of time was a mystery; a time without calendars and without timepieces such as sun dials, clocks, and watches. Humans have a craving for knowing the time and the date. How many times do you refer to your watch or to a calendar? Could you exist without these devices in today’s world? If you had no timepiece or calendar, how would you go about keeping track of time and the recording of time?

These same cravings and needs faced the early peoples of our world. Initially they had to know the seasons so they could prepare for cold weather, rainy weather, hunting times, planting of seeds, harvesting of produce, primitive religious observances, etc. As primitive peoples broadened their horizons and became involved in trade and commerce, there was a need for calendars for civil purposes such as the arranging of contracts, the paying of rents and debts, the recording of these and other civil events.

Early peoples quickly realized that nature provided devices for the keeping of time; the phases of the moon, the sun; the planets, the stars, the phases of the seasons; the cyclical changes in the amount of daylight that followed the phases of the seasons.

Various cultures produced methods of time reckoning. A number of these cultures had prominent places in establishing our present calendar and method of time keeping. Their methods, based on the earlier findings of other cultures, provided the foundation of our present calendar.

A brief chronology of our calendar is shown in Figure 1.

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Figure 1 Brief Chronology of Our Calendar

Development of Days, Months, and Years Most cultures counted days and how many days there were in one phase of the moon and how many moon phases there were before the seasonal cycle recurred. More advanced cultures observed the equinoxes, the solstices, and the repeated cycle of the position of certain stars. This gave us three important divisions for our calendar; the day based on the revolution of the earth around its axis, the month based on the movement of the moon around the earth, and the year based on the orbit of the earth around the sun. But, nature does not understand mathematics and the human need for precise values.

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There are 29 days, 12 hours, 44 minutes, 2.9 seconds, or 29.5305889 days in a moon cycle measured from full moon to full moon and 365 days, 5 hours, 48 minutes, 45.19 seconds, or 365.2421897 days in an earth cycle around the sun measured from vernal equinox to vernal equinox.

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Page 2 Thus there are not an exact number of days in a moon cycle or month and there are not an exact number of moon cycles in a sun cycle or year. This does not make it easy for a calendar designer especially the early designers who could not calculate these periods to the accuracy of to-day.

Because the number of days in a moon cycle does not divide evenly into a year, some early societies divided the year into 12 months which was short of a year and some divided the year into 13 months which was too long. Our present calendar uses 12 months with all months except February being longer than a moon cycle.

Development of Hours, Minutes, and Seconds The Sumerians divided the days into hours using two systems. In one, the day commenced at midnight and had six main divisions; each divided into 60 parts. In the other, the day commenced at sunset and had 12 main divisions; each divided into 30 parts.

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Number of hours in a day originated with the Sumerians who had two methods: 1. The day commenced at midnight and had 6 main divisions with 60 subdivisions. 2. The day commenced at sunset with 12 main divisions with 30 subdivisions.

The Babylonians modified the Sumerian system: The day commenced at sunrise and had 24 main divisions with 60 subdivisions and 60 sub-subdivisions.

The second method of the Sumerians was adopted by the ancient Greeks with a further subdivision of the 30 parts into 60 finer parts. The Babylonians modified the Sumerian systems by dividing the day into 24 hours starting at sunrise.

The reason for choosing 24 and 60 is lost in antiquity but there are a number of theories. One popular theory suggests that the choice was based on the fact that 24 and 60 are evenly divisible by 2, 3, and 4 and 60 is also evenly divisible by 5.

People liked to be able to take halves, thirds, and quarters of things and have whole number results. This is not simple in a decimal system. In our own experience we have had to deal with dozen, score, and gross that are based on older counting systems. The Babylonian numbering system is still with us, not only for time, but for geometry and navigation where the circle is divided into 360 degrees, subdivided into 60 minutes, and subdivided again into 60 seconds. These early systems also did not benefit from a full understanding of the concept of zero. This also affected the development of our present day calendar.

Rome and Italy, throughout the middle ages, used a 24-hour day starting at sunset. The Persians used 24 hours starting at sunrise. In South Germany the day consisted of two

Page 3 cycles of 12 hours each starting at midnight and this was incorporated into clocks which became fairly common around 1400 CE Because sunset and sunrise occur at different times each day, the idea of using the fixed reference of 12 midnight for the start of each day made sense and was incorporated into clocks and watches. The idea of using two 12- hour periods rather than one 24-hour period also made the construction of time pieces somewhat easier.

Development of the Week and the Naming of the Days The concept of a week came from the number of days between market days. This varied between groups of primitive peoples from four days to ten days.

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Our present week is based on the 7 day week that comes down to us through the Israelites who based their week on that of the Babylonians and the Sumerians.

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Early civilizations attached some mystical significance to the number 7. Support for this may have derived from the then known solar system bodies of the sun, the moon and 5 planets.

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The names of the days of the week derive from these seven bodies in the solar system. Table 1 shows the presently used names for the days of the week and from whence the names are derived.

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Table 1: Derivation of the Names of the Days in a Week

Solar Body Latin French Saxon English (from the solar (from the Latin) (from the solar (from the Saxon) body or the god body or the god representing that representing that body) body) Sun Dies Dominicus Dimanche Sun’s Day Sunday (Day of the Lord)* Moon Dies Lunae Lundi Moon’s Day Monday Mars Dies Martis Mardi Tiu’s Day Tuesday Mercury Dies Mercurii Mercredi Woden’s Day Wednesday Jupiter Dies Jovis Jeudi Thor’s Day Thursday Venus Dies Veneris Vendredi Freya’s Day Friday Saturn Dies Saturni Samedi Saterne’s Day Saturday * The French derives from the fact that Sunday is the day of the Lord.

Page 4 Development of the Roman Calendar Our present calendar, with its peculiar arrangement of months with no apparent reason for the number of days in each, is based on the Roman calendar and the variations it went through over the centuries. To understand to-day’s calendar we must look at its roots in the Roman calendar.

The first Roman calendar was introduced by Romulus sometime prior to 700 BCE (Roman year 53). It consisted of 10 months with the start of the year being based on the vernal equinox that was considered to occur on the 25th day of Martius (March). The names of the months and the days in each month are shown in Table 2.

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Table 2: Romulus Calendar (prior to 700 BCE or Roman year 53)

Month No. of Days Martius 31 Aprilis 30 Maius 31 Iunius 30 Quintilis 31 Sextilis 30 Septembris 30 Octobris 31 Novembris 30 Decembris 30 TOTAL 304

The first four months were named after Roman gods and the last six months were named for their numerical position five through ten. The remaining days between December and the following March were unnamed. One, two, or three intercalary months were added indiscriminately when it was noticed that the calendar and the seasons were getting out of line.

Sometime during the reign of the second king of Rome, Numa Pompilius (715 to 673 BCE or Roman years 38 to 80) two more months named after gods were added after December as shown in Table 3.

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Page 5 Table 3: Numa Pompilius Calendar (during his reign 715 to 673 BCE or Roman years 38 to 80)

Month No. of Days Martius 31 Aprilis 29 Maius 31 Iunius 29 Quintilis 31 Sextilis 29 Septembris 29 Octobris 31 Novembris 29 Decembris 29 Ianuarius 29 Februarius 28 TOTAL 355

You will note that some of the months had fewer days than in the Romulus calendar in order to provide enough days to incorporate two more months. This calendar year was short of a full year by 10.25 days and this became obvious as time went by because the equinoxes and solstices were moving relative to the calendar.

The 5th king of Rome, Torquinius Priscius (616 to 579 BCE or Roman years 137 to 174) corrected this apparent movement of the seasons with his version of the calendar as shown in Table 4.

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Table 4: Roman Republican Calendar Introduced by Torquinius Priscius (616 to 579 BCE or Roman years 137 to 174)

1st and 3rd Years 2nd Year 4th Year Month No. of Month No. of Month No. of Days Days Days Martius 31 Martius 31 Martius 31 Aprilis 29 Aprilis 29 Aprilis 29 Maius 31 Maius 31 Maius 31 Iunius 29 Iunius 29 Iunius 29 Quintilis 31 Quintilis 31 Quintilis 31 Sextilis 29 Sextilis 29 Sextilis 29 Septembris 29 Septembris 29 Septembris 29 Octobris 31 Octobris 31 Octobris 31 Novembris 29 Novembris 29 Novembris 29 Decembris 29 Decembris 29 Decembris 29 Ianuarius 29 Ianuarius 29 Ianuarius 29 Februarius 28 Februarius 23 Februarius 23 Intercalens 27 Intercalens 28 TOTAL 355 TOTAL 377 TOTAL 378

This calendar made some attempt at averaging the number of days over a four year period to be 366.25 days, one day too much. He did this by adding an extra month every second and fourth year starting on the sixth day before the month of Martius or by our calendar on the 24th of February. The balance of February in those years was left out. The number of days in the other months remained unchanged and the extra months had the unofficial name of Intercalens that means “between months”.

Torquinius Pricius also tried unsuccessfully to introduce the idea of January as the first month of the year because January contained the festival of the god of gates or god of beginnings. It was not until 153 BCE that his idea was incorporated in the Roman Republican calendar and the 1st of January became New Year’s Day instead of the 25th of March. Table 5 shows the new arrangement of the months.

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Table 5: Roman Republican Calendar for 153 to 47 B.C or Roman years 600 to 706

1st and 3rd Years 2nd Year 4th Year Month No. of Month No. of Month No. of Days Days Days Ianuarius 29 Ianuarius 29 Ianuarius 29 Februarius 28 Februarius 23 Februarius 23 Martius 31 Intercalens 27 Intercalens 28 Aprilis 29 Martius 31 Martius 31 Maius 31 Aprilis 29 Aprilis 29 Iunius 29 Maius 31 Maius 31 Quintilis 31 Iunius 29 Iunius 29 Sextilis 29 Quintilis 31 Quintilis 31 Septembris 29 Sextilis 29 Sextilis 29 Octobris 31 Septembris 29 Septembris 29 Novembris 29 Octobris 31 Octobris 31 Decembris 29 Novembris 29 Novembris 29 Decembris 29 Decembris 29 TOTAL 355 TOTAL 377 TOTAL 378

This version did not change the number of days in any given month or the four-year average of 366.25 days in a year. This calendar was accepted in most but not all of the Roman Empire. England and Scotland were two exceptions as they continued with New Year’s Day as the 25th of March until 1600 in Scotland and 1752 in England.

The Roman calendar also had an unusual way of identifying the days in each month. The Romans did not number the days of the month starting with the first day but numbered the days as being so many days before the first day of the next month. The Romans used the first day of the month as the day for paying rents, paying debts, finalizing contracts, etc. and so found it easier to know how many days they had left before meeting the obligation of the following month. The first of each month was called Kalendis that derives from the word calendrium meaning account book. Our word calendar in turn derives from this.

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The Roman month was further broken down with two special days, the Idibus (Ides in English) and the Nonis (Nones in English). The Idibus was based on the occurrence of the full moon and was fixed at either the 13th day or the 15th day depending on the month. In the months of Martius, Maius, Quintilis, and Octobris the Nonis occurred on the 7th day and the Idibus occurred on the 15th day. In all the other months the Nonis occurred on the 5th day and the Idibus occurred on the 13th day. The Nonis based on the occurrence of the first quarter of the moon and was fixed at nine days before the Idibus.

The days leading up to the Idibus or Nonis were identified as so many days before the Idibus or Nonis. As the Romans used inclusive counting, the day before a Kalendis, an

Page 8 Idibus, or a Nonis was counted as the second day before. As this calendar would involve a very large table to explain a full year, Table 6 provides an example using the month of Maius (May).

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Table 6: The Month of Maius (May) in the Roman Calendar

Present Day Maius Translation Numbering 1st of May Kalendis Maius 1st of May 2nd of May Postridie Kalendas Maius Day after 1st of May 3rd of May Ante Diem V Nonas Maius 5th day before Nones of May 4th of May Ante Diem IV Nonas Maius 4th day before Nones of May 5th of May Ante Diem III Nonas Maius 3rd day before Nones of May 6th of May Pridie Nonis Maius Day before Nones of May 7th of May Nonis Maius Nones of May 8th of May Ante Diem VIII Idus Maius 8th day before Ides of May 9th of May Ante Diem VII Idus Maius 7th day before Ides of May 10th of May Ante Diem VI Idus Maius 6th day before Ides of May 11th of May Ante Diem V Idus Maius 5th day before Ides of May 12th of May Ante Diem IV Idus Maius 4th day before Ides of May 13th of May Ante Diem III Idus Maius 3rd day before Ides of May 14th of May Pridie Idus Maius Day before Ides of May 15th of May Idibus Maius Ides of May 16th of May Ante Diem XVII Kalendas Iunius 17th day before 1st of June 17th of May Ante Diem XVI Kalendas Iunius 16th day before 1st of June 18th of May Ante Diem XV Kalendas Iunius 15th day before 1st of June 19th of May Ante Diem XIV Kalendas Iunius 14th day before 1st of June 20th of May Ante Diem XIII Kalendas Iunius 13th day before 1st of June 21st of May Ante Diem XII Kalendas Iunius 12th day before 1st of June 22nd of May Ante Diem XI Kalendas Iunius 11th day before 1st of June 23rd of May Ante Diem X Kalendas Iunius 10th day before 1st of June 24th of May Ante Diem IX Kalendas Iunius 9th day before 1st of June 25th of May Ante Diem VIII Kalendas Iunius 8th day before 1st of June 26th of May Ante Diem VII Kalendas Iunius 7th day before 1st of June 27th of May Ante Diem VI Kalendas Iunius 6th day before 1st of June 28th of May Ante Diem V Kalendas Iunius 5th day before 1st of June 29th of May Ante Diem IV Kalendas Iunius 4th day before 1st of June 30th of May Ante Diem III Kalendas Iunius 3rd day before 1st of June 31st of May Pridie Kalendas Iunius Day before 1st of June

Leading up to 46 BCE or Roman year 707 Julius Caesar called on the Egyptian scholar Sosigenes of Alexandria to bring the Roman calendar in line with the seasons as it had once again drifted so that the equinoxes and solstices were not in the correct locations. In 46 BCE or Roman year 707, following Sosigenes’ calculations, Julius Caesar decreed that three Intercalens were to be added making that year 425 days long to bring the equinoxes and solstices back in line. See Table 7.

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Table 7: Julian Calendar of 46 BCE or Roman year 707

Month No. of Days Ianuarius 29 Februarius 23 Intercalens 28 Martius 31 Aprilis 29 Maius 31 Iunius 29 Quintilis 31 Sextilis 29 Septembris 29 Octobris 31 Intercalens 23 Intercalens 24 Novembris 29 Decembris 29 TOTAL 425

Sosigenes reckoned fairly accurately for his time, that the year was 365.25 days long. He added the concept that every 4th year should have an extra day so that on average the calendar would be accurate forever. Unknown to him the year is actually 365 days, 5 hours, 48 minutes, 45.19 seconds, or 365.2421897 days long. Because of our present day reliance on accurate time keeping, the accumulated fractions of a second are taken care of by every so often introducing a leap second.

Sosigenes also suggested that the days of the months alternate 31 and 30 which gives a total of 366 days as shown in the leap year column of Table 8.

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Table 8: Julian Calendar for 45 to 9 BCE or Roman years 708 to 744

Regular Year Leap Year Length of Month No. of Month No. of Half Year Quarter Days Days Year Ianuarius 31 Ianuarius 31 90 Februarius 29 Februarius 30 or Martius 31 Martius 31 181 91 Aprilis 30 Aprilis 30 or Maius 31 Maius 31 182 91 Iunius 30 Iunius 30 Iulius 31 Iulius 31 Sextilis 30 Sextilis 30 91 Septembris 31 Septembris 31 Octobris 30 Octobris 30 182 Novembris 31 Novembris 31 91 Decembris 30 Decembris 30 TOTAL 365 TOTAL 366

A total of 366 days was fine for a leap year so an extra day in regular years was dropped from Februarius as it was the month most unfavourable to the Romans. It was known as the month of the dead when those who had died during the winter were buried. This produced a well-balanced calendar and when introduced the old fifth month of Quintilis was renamed Iulius in honour of Julius Caesar who had initiated the calendar reform.

This calendar was known as the Julian calendar in honour of Julius Caesar. This is not to be confused with the Julian Day Calendar that sequentially numbers the days of the year starting with the first of January each year. This misnomer was introduced by some who were not knowledgeable but the misnomer and confusion continues to this day.

Immediately following the introduction of the Julian calendar, things went wrong. The Romans had no concept of zero and thus counted inclusively. Using our present decade as an example the Romans would count “one” at the beginning of 2004 and would count “two” at the end of that year. After three years when they counted “four” in 2007 they would then considered themselves in the fourth year and insert a leap year, one year ahead of the time recommended by Sosigenes. Figure 2 demonstrates the difference in thinking between the Romans and Sosigenes.

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Figure 2: Misinterpretation of Sosigenes Rule for Leap Years Using Our Present Decade as an Example

In 8 BCE (Roman year 745) it was brought to the attention of Caesar Augustus that once again the equinoxes and solstices had moved. He corrected this by decreeing that there would be no leap years until 4 CE (Roman year 756) to eliminate the three extra days that had accrued due to the improper application of the leap year rule.

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In honour of Caesar Augustus, the old sixth month of Sextilis was renamed Augustus. The Romans were superstitious about even numbers that were thought to bring bad luck so the month of Augustus was given 31 days instead of 30. This created three months in a row with 31 days so the Romans changed the remaining months after the month of Augustus to alternate 30 and 31. This added up to 366 days in a regular year and 367 days in a leap year. To correct this the unfavourable month of Februarius, once again lost a day, one in a regular year and one in a leap year. This is how we came to have to-day’s calendar with its peculiar arrangement of lengths of the months. Table 9 demonstrates this.

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Table 9: Julian Calendar for 8 BCE or Roman year 745 to To-day

Regular Year Leap Year Length of Month No. of Month No. of Half Year Quarter Days Days Year Ianuarius 31 Ianuarius 31 90 Februarius 28 Februarius 29 or Martius 31 Martius 31 181 91 Aprilis 30 Aprilis 30 or Maius 31 Maius 31 182 91 Iunius 30 Iunius 30 Iulius 31 Iulius 31 Augustus 31 Augustus 31 92 Septembris 30 Septembris 30 Octobris 31 Octobris 31 184 Novembris 30 Novembris 30 92 Decembris 31 Decembris 31 TOTAL 365 TOTAL 366

The well balanced calendar of Sosigenes is now lost in antiquity and we are left with a calendar that has two sets of consecutive months with 31 days, July and August, and December and January and a month of February that is obviously out of line with the others. For those who like to divide the year into halves and quarters the calendar of to- day makes it difficult whereas the calendar of Sosigenes made it quite simple. We can see this when we compare Table 8 with Table 9.

In the Roman calendar leap year the extra day in Februarius was added by doubling up the Ante Diem VI Kalendis Martius (6th day before the 1st of March) as shown in Table 10. This resulting in the terms “bisextile month” and “bisextile year” when referring to a leap year.

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Page 13 Table 10: The Month of Februarius (February) in a Leap Year in the Roman Calendar

Present Day Februarius Translation Numbering 1st of February Kalendis Februarius 1st of February 2nd of February Postridie Kalendas Februarius Day after 1st of February 3rd of February Ante Diem IV Nonas Februarius 4th day before Nones of February 4th of February Ante Diem III Nonas Februarius 3rd day before Nones of February 5th of February Nonis Februarius Nones of February 6th of February Ante Diem VIII Idus Februarius 8th day before Ides of February 7th of February Ante Diem VII Idus Februarius 7th day before Ides of February 8th of February Ante Diem VI Idus Februarius 6th day before Ides of February 9th of February Ante Diem V Idus Februarius 5th day before Ides of February 10th of February Ante Diem IV Idus Februarius 4th day before Ides of February 11th of February Ante Diem III Idus Februarius 3rd day before Ides of February 12th of February Pridie Idus Februarius Day before Ides of February 13th of February Idibus Februarius Ides of February 14th of February Ante Diem XVII Kalendas Martius 17th day before 1st of March 15th of February Ante Diem XVI Kalendas Martius 16th day before 1st of March 16th of February Ante Diem XV Kalendas Martius 15th day before 1st of March 17th of February Ante Diem XIV Kalendas Martius 14th day before 1st of March 18th of February Ante Diem XIII Kalendas Martius 13th day before 1st of March 19th of February Ante Diem XII Kalendas Martius 12th day before 1st of March 20th of February Ante Diem XI Kalendas Martius 11th day before 1st of March 21st of February Ante Diem X Kalendas Martius 10th day before 1st of March 22nd of February Ante Diem IX Kalendas Martius 9th day before 1st of March 23rd of February Ante Diem VIII Kalendas Martius 8th day before 1st of March 24th of February Ante Diem VII Kalendas Martius 7th day before 1st of March 25th of February Ante Diem VI Kalendas Martius 6th day before 1st of March 26th of February Ante Diem VI Kalendas Martius 6th day before 1st of March 27th of February Ante Diem V Kalendas Martius 5th day before 1st of March 28th of February Ante Diem IV Kalendas Martius 4th day before 1st of March 29th of February Ante Diem III Kalendas Martius 3rd day before 1st of March 30th of February Pridie Kalendas Martius Day before 1st of March

Development of the Gregorian Calendar

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Because the length of the year is 365.2421897 days the Julian calendar, even with leap years included, would develop an error of one whole day every 128 years. This error became more obvious and was noted as being three days by the Bede of the English monastery of Jarrow in 730 CE In the 13th century it was noted by two English scientists, Johannes de Sacrobosco and Roger Bacon that the error by this time totaled seven days. It was not until the 16th century that a further correction to the calendar was made.

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Luigi Lilio a lecturer in medical science at the University of Perugia, Italy developed a set of rules for a new calendar. Ten years later and sometime after his death, his brother Antonio Lilio presented the ideas for this calendar to Pope Gregory XIII.

In March of 1582 Pope Gregory XIII approached the governments of the principle states of the Holy Roman Empire to get their agreement to correct the calendar. To prevent the calendar and the equinoxes and solstices getting too far out of alignment, the following rules were adopted:

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• Every year evenly divisible by four shall have one extra day - a leap year • Every year evenly divisible by 100 shall not have that one extra day - not a leap year • Every year evenly divisible by 400 shall have one extra day - a leap year

It was important to the Roman Catholic Church to keep the vernal equinox and the calendar aligned because the date of Easter is tied in with the date of the vernal equinox; but this is another topic too lengthy to discuss here.

To correct the calendar that was now out by ten days, Pope Gregory directed that the day following the feast of St. Francis, the 5th of October 1582, should be the 15th of October and that New Year’s Day would be the 1st of January commencing in the year 1583. Not only did 1582 loose 10 days but it was also shortened by an additional 83 days because it started on 25th March and ended on 31 December.

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With these new rules the old Julian calendar became known as the Gregorian calendar. Following the above rules with the Gregorian calendar the years 1600 and 2000 were leap years whereas the years 1700, 1800, and 1900 were not leap years.

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A further correction may be required in 4000 CE Based on today’s knowledge of the Earth’s orbit and taking into account the projected slowing down of the Earth’s orbit the Gregorian calendar will be behind the actual year by an amount in the range of 0.8 to 1.1 days providing nothing catastrophic occurs to change our rotation around the sun. This will require 4000 CE to be a leap year.

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The majority of Roman Catholic countries followed the decree of Pope Gregory but the Protestant and Orthodox countries tenaciously held onto the old Julian calendar. During

Page 15 the 1700s the various Protestant countries gradually began to accept the Gregorian calendar but by now the error had grown to 11 days.

Great Britain adopted the Gregorian calendar in 1751. An act of parliament decreed that the day following the 2nd of September 1752 should be the 14th of September. The same act stated that the New Year should be the 1st of January instead of 25 March commencing in the year 1752. This change of New Year’s Day had already been enacted in Scotland as early as 1600.

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To avoid the obvious confusion this could cause, some people and some institutions used a double dating system where the date was written using both the Julian calendar and the Gregorian calendar.

As an example let us say that you had an ancestor was born around the end of January or beginning of February during the period of multiple calendars. If he was Roman Catholic he would have used the Gregorian calendar. If he was Protestant he would have used the Julian calendar but the year of his birth would have depended on whether he was born in England or Scotland. An example of the same date expressed in the three ways identified above would be:

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• Gregorian Calendar - 1 February 1750 (11 days later than in the Julian Calendar) • Julian Calendar used in England - 21 January 1749 (New Year’s Day was 25th March) • Julian Calendar used in Scotland - 21 January 1750 (New Year’s Day was 1st January).

Also be wary of Julian calendar dates in the years 1599 in Scotland and 1751 in England because those years started on 25th March but ended on 31 December. You can now see why it is important for genealogists to know and understand the calendars in use in the British Isles during the period from 1582 to 1752.

Further developments

The Earth is slowing down in its orbit around the Sun requiring the addition of leap seconds every so often. This is important in our present digital age where World communications rely heavily on precise timing. Leap seconds have been added starting in 1972 and at present total 24 extra seconds that have been added since then. The addition of leap seconds is not a linear relationship as it depends on the interaction of the various planets, satellites, and the sun. Table 11 shows the addition of these leap seconds.

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Table 11: Single Seconds Added to Our Universal Time as Needed

Date Total Date Total Date Total Date Total Secs Secs Secs Secs 30 Jun 1972 1 30 Jun 1981 10 31 Dec 1990 16 31 Dec 2005 23 31 Dec 1972 2 30 Jun 1982 11 30 Jun 1992 17 31 Dec 2008 24 31 Dec 1973 3 30 Jun 1983 12 30 Jun 1993 18 31 Dec 1974 4 30 Jun 1985 13 30 Jun 1994 19 31 Dec 1975 5 31 Dec 1987 14 31 Dec 1995 20 31 Dec 1976 6 31 Dec 1989 15 30 Jun 1997 21 31 Dec 1977 7 31 Dec 1998 22 31 Dec 1978 8 31 Dec 1979 9

Other Calendars

There are about 40 different calendars in use throughout the world at present. Most of these calendars are for religious observances with a few being used for commercial use within the bounds of the particular country or religious group.

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For international purposes we use the Gregorian calendar although there are various groups trying to promote calendar reform.

One calendar reform that existed for a short time was the calendar of the French Republic that was introduced in 1793 and was last used in Paris in 1871. It had 12 months of 30 days with all months being renamed to suit the seasons. Each month consisted of 3 weeks of 10 days. Five days of national holiday were given at the end of each year (six in a leap year). The clocks were redesigned to have 10 hours in a day, 100 minutes in an hour, and 100 seconds in a minute. The clock redesign was suspended in 1795.

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The various Orthodox countries gradually adopted the Gregorian calendar for civil use but continued using the Julian calendar for religious observances. On 14 September 2010 the Eastern Orthodox churches celebrate New Year’s Day as 1 September in the year 7519. As their calendar is now 13 days ahead of the Gregorian calendar, they celebrate Christmas on 7 January.

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The Hebrew calendar is a lunar calendar that repeats every 19 years. In order to keep the months and religious observances in keeping with the seasons, seven intercalary months are added in each 19 year cycle. The Hebrew year 5770 began at sundown 18 September 2009 and ends 8 September 2010.

Page 17 Conclusion

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I have just barely scratched the surface of this interesting subject. Many countries, cultures, and religions still use their own calendars but internationally we now use the Gregorian calendar of 1582.

Bibliography

Encyclopedia Britannica Royal Greenwich Observatory web site http://greenwichmeantime.com/ National Institute of Standards and Technology (NIST) Physics Laboratory web site http://www.nist.gov/physlab World Almanac Scientific American New Scientist

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