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The History of the Gregorian Calendar

The History of the Gregorian Calendar. Ed Staples. Close up of My Watch. Lunar or Solar?. The story of the calendar is essentially centred around the three natural cycles of the daily sun rise, the lunar cycle, and the tropical year. . The 7 day week.

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The History of the Gregorian Calendar

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  1. The History of the Gregorian Calendar Ed Staples

  2. Close up of My Watch

  3. Lunar or Solar? • The story of the calendar is essentially centred around the three natural cycles of the daily sun rise, the lunar cycle, and the tropical year.

  4. The 7 day week • The seven day week has no natural markers. It is an intellectual creation and does not fit well with the lunar or solar calendar.

  5. Check your salary!

  6. Check your salary! Because there are 313 fortnights in 12 years

  7. 1st Roman Calendar: Romulus 753 BC

  8. Changes by King Numa: 7th Century BC Lunar Calendar

  9. Beware the ides of March!

  10. 1st Attempt to align with seasons: Numa 2

  11. Julius Caesar 46BC (Sosigenes) The Julian Calendar

  12. Caesar’s adjustment to the vernal equinox

  13. 432BC : The Metonic Cycle (Greece) • 235 Lunations is virtually identical to 19 Tropical Years

  14. Golden numbers still used to determine date of Easter Sunday Golden numbers

  15. Solar year re-calculated as 365.2219 years

  16. Go to the Equator – look East E W

  17. Solstice – Sun in Capricorn

  18. equinox

  19. Solstice – Sun in Cancer

  20. equinox

  21. Solstice – Sun in Capricorn

  22. Like a coil of rope Solstice Solstice EAST

  23. The precise moment of the equinox East

  24. Walking south to Canberra Lat:35S • If we walk south back to Canberra from the equator, the rising vertical star lines will appear to lean away from us (lean toward the north) • This is because we are on a spherical earth

  25. Canberra Sun rising Lat 90 - Lat East North South

  26. Motion of the Sun over the year Lat North South

  27. Looking East in Canberra

  28. Looking South in Canberra Canberra Latitude 35 degrees South

  29. The equatorial ring 90 - Lat

  30. The equatorial ring 90 - Lat

  31. The equatorial ring 90 - Lat

  32. The equatorial ring 90 - Lat

  33. The equatorial ring Shadow falls Equinox point 90 - Lat

  34. The equatorial ring Shadow falls Post Equinox point 90 - Lat

  35. Equinox by Sundial? The, shadow is shortest in Summer and longest in winter, so at some stage in its “vertical” journey, the shadow tip will touch the equinox line. (twice a year )

  36. A Canberra Sundial (35 deg gnomon) Winter Solstice Equinox line Summer Solstice

  37. Hence…. • Actual Tropical Year 365.24219 days • Julian assumption 365.25 days • Difference 0.00781 days • (Spotted by the Venerable Bede in AD 725

  38. Do the Maths! • 0.00781 X 24 X 60 = 11 minutes and 15 seconds

  39. How the small difference accrues

  40. Luigi Lilio’s solution

  41. Pope Gregory: 1582 (Lilio) The Gregorian calendar

  42. The UK experience 1751

  43. 10 minute break

  44. Zeller 1883

  45. Conway’s Doomsday

  46. Corrections

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