Monthly Archives: December 2016

Leap-second on December 31, 2016


Ed. Note:  Did you know that today, December 31, 2016, will be longer by one additional second? By the time most of you read this post, it will already have been done. Happy New Year!

From Larry Sessions in EarthSky HUMAN WORLD | December 31, 2016, “Leap second to be added tonight”

Why do we need a leap second? Isn’t the length of our day set by the rotation of the Earth? Like the ancients who insisted that all motion in the heavens must be perfect, uniform and unvarying, many of us today assume that the Earth’s rotation – its spin on its axis – is perfectly steady. We learned, correctly, that the sun, moon, stars and planets parade across our sky because the Earth turns. So it is easy to understand why we assume that the Earth’s rotation is precise and unwavering. Yet Earth’s rotation does not stay perfectly steady.

See why below:

From the U.S. Naval Observatory,

2016 will drag on for just a bit longer than most other years. Yes, it has already stretched an extra day in length thanks to the rules of the Gregorian Calendar which deem it to be a leap-year, but thanks to our modern precision timekeeping methods it will get one extra second added to its length in the last minute before the strike of 00 hours, 00 minutes, and 00 seconds Coordinated Universal Time (UTC) on January 1st, 2017.

This “leap second” is necessary due to the gradual slowing of the Earth’s rotation when compared to the ultra-precise atomic time scale known as International Atomic Time (TAI) that is now observed around the globe. Since 1972 our civil time has been based on TAI, whose second is defined by a very precise atomic frequency. This time-scale exists coincidentally with another, known as UT1, which closely mirrors the length of the mean time between successive transits of the Sun over a standard meridian.

Currently the difference between these two time-scales amounts to about 0.0015 to 0.002 seconds per day, resulting in a cumulative difference between TAI and UT1 of one second over the span of a few years, and when the difference approaches one full second a “leap second” is inserted to coordinate the two time-scales for another few years.

The actual date of insertion for a given “leap second” is based on observations carried out in part by the USNO’s Earth Orientation Department, which keeps close tabs on how the Earth rotates with respect to a distant reference frame made up of thousands of very distant quasars [like those in the Hubble image below]. While 2016 will amount to an extra-log year, at least it won’t be like 1972, which saw the insertion of two “leap seconds” in addition to being a leap year.



Winter Solstice 2016 at Kanayama Megaliths


Iwaya-Iwakage blogsite for Kanayama Megaliths has three new posts reporting on winter solstice  there. On December 21, 2016, a group of intrepid souls made the steep ascent up Higashinoyama (the peak shown in above photo by S. Tokuda) in the early hours to view the light of the rising sun. Join them on this winter adventure in the mountains of Kanayama.



Early December at Kanayama Megaliths

Iwaya-Iwakage of Kanayama Megaliths


We have translated the brand-new post of December 06, 2016 at

金山巨石群 12月初め  Kanayama Megaliths Early December

12月 2日(金)   December 2 (Friday)

Fine weather today. Visitors in the morning and afternoon.


The 10 o’clock tour is recommended when visiting Kanayama Megaliths in winter because the morning sun emerges from the mountain around 10 am. The cooling of the previous night still continues into the morning.


From the lower megalith site (Iwaya-Iwakage and Senkoku-Ishi) we can see the sun  shining on Higashinoyama Eastern Mountain at around 9:15 in the morning.


Here at the lower megalith site, it is still cold. However light is beginning to hit the mountain in the back of the lower site.

On this day there were four people in the group from 9:50 to 12:30. Winter showtime at Iwaya-Iwakage: about 10 o’clock, the morning sun gradually enters inside. A movie would allow you to…

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Beginning of Early Winter at Higashinoyama

Iwaya-Iwakage of Kanayama Megaliths


The Japanese Kanayama Megaliths blogsite has just made two new posts about the beginning of the winter season (Early Winter in the Kanayama Solar Calendar is the approximate sixty-day period prior to the winter solstice). Here is an excerpt from the post dated 2016.12.04, with permission. The original post in Japanese is:


金山巨石群 冬期の始まり   Beginning of Early Winter at Kanayama Megaliths

In the Kanayama Megaliths solar calendar, wintertime begins on about 10/23. This is similar to the calendar of ancient Egypt.

朝の観測 Morning observation

For the first observation of the Early Winter season we went mountain climbing to Higashinoyama (Higashi-no-yama, Eastern Mountain) megalith group. This year at 8:30, a total of five people departed from Iwaya-Iwakage site. Here are some photos taken when we reached the peak.

When reaching the top ridge, a little down the slope on the south side, two megaliths of 9 meters long appear side…

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