navy.mil: Leap secondsArkiveret 11. juni 2012 hos Wayback Machine Citat: "...The Earth is constantly undergoing a deceleration caused by the braking action of the tides...The length of the mean solar day has increased by roughly 2 milliseconds since it was exactly 86,400 seconds of atomic time about 1.79 centuries ago (i.e. the 179 year difference between 1999 and 1820). That is, the length of the mean solar day is at present about 86,400.002 seconds instead of exactly 86,400 seconds..."
National University of Singapore, GEK1506 Heavenly Mathematics: Highlights of Cultural Astronomy Citat: "...However, the Mayans did not use the leap year concept as the Gregorian calendar does. Instead, they just keep track of the errors in the calendar...The Mayans actually chose a certain date to record this calculated errors. They chose the date 4 Ahau 8 Cumku that repeated every 52 haab years. During each of this repetition, they would calculate the accumulated error and
record it on a stela..."
Frequently Asked Questions about Calendars, Version 2.9, Claus Tøndering, 4 April 2008: 9. The Maya Calendar Citat: "...We can therefore derive a value for the Mayan estimate of the year by dividing 1,101,600 by 365, subtracting 2, and taking that number and dividing 1,101,600 by the result, which gives us an answer of 365.242036 days, which is slightly more accurate than the 365.2425 days of the Gregorian calendar...(This apparent accuracy could, however, be a simple coincidence...)..."
navy.mil: Leap secondsArkiveret 11. juni 2012 hos Wayback Machine Citat: "...The Earth is constantly undergoing a deceleration caused by the braking action of the tides...The length of the mean solar day has increased by roughly 2 milliseconds since it was exactly 86,400 seconds of atomic time about 1.79 centuries ago (i.e. the 179 year difference between 1999 and 1820). That is, the length of the mean solar day is at present about 86,400.002 seconds instead of exactly 86,400 seconds..."
Mesoamerican Calendars Citat: "...Finally, many other Mesoamerican cultures, notably the Olmecs who are credited with the invention of the Mesoamerican calendar, had adopted similar calendars as the Mayas and the Aztecs. Such was the case of the Zapotecs, Mixtecs, Otomies, Tarascans, and many others, some of which continued to preserve their calendar. [1,2]...The Tarascans or Purepecha had a similar calendar as the Aztecs, but started the year on different days..."
