No, it has not begun a new decade, no one more than some media outlets insist on it: 2020 is the last year of the second decade of the 21st century, which, by the way, began on January 1, 2001. In the case of decades, confusion has much to do with the widespread habit of naming them by the figures of the tens, as in the well-known expression "the merry twenties", which seems to include all the years that have a 2 in that place, from 1920 to 1929 both inclusive.
Since the decade is not an official temporary unit of measure (we do not say that we are in the ICC A.D. decade), this confusion is irrelevant, and it is even lawful to call a decade to any ten-year period, for example, from the end of World War II to the mid-1950s (although in this case it is more correct to use the term "decade"). But in the case of centuries the error is inadmissible, and it is hard to believe that it still persists,
The numbers of the abcabc form are divisible by 1001, and 1001 x 11 x 13 x 7, which allows you to perform an amazing "math" trick
In terms of the numbers of the form abab, as 2020, do not possess any special property. Yes they have it those of the form abcabc, because they are divisible by 1001, and 1001 x 11 x 13 x 7, which allows to perform an amazing trick of matemagia:
One of those present is asked to write on a piece of paper a three-digit number and then pass the paper to another person, who will then have to repeat the same three figures. A third person is asked to divide by 11 the resulting six-figure number, and the quotient will be divided by 13 by a fourth person, and the result will be divided by 7 by a fifth, which will pass the final result to the matemago, which will guess the initial number (which is none other than the last quotient). Repeating the three digits is equivalent to multiplying the number by 1001, and as then divided by 1001, you get the initial number again.
Total eclipse and annular eclipse
As an example of media layoffover over the decades, the recent solar eclipse of December 26 was repeatedly announced as "the last eclipse of the decade", a title that actually corresponds to the one that will occur on December 14, 2020.
What maximum width could a ring of fire be
December 26 was, by the way, an annular eclipse, named after the spectacular "ring of fire" seen around the lunar disc when its center coincides with that of the solar disc. Why does this ring look in some eclipses and others not?
remember that, rounding, the diameter of the Moon is 3,500 km, and its distance to Earth ranges between 360,000 km and 400,000 km. The diameter of the Sun is 1.4 million km, and its distance to Earth varies between 147 and 152 million kilometers.