During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their numbered year on 1 January while others were still using some other date. Even before 1582, the year sometimes had to be double dated because of the different beginnings of the year in various countries. Woolley, writing in his biography of John Dee (15271608/9), notes that immediately after 1582 English letter writers "customarily" used "two dates" on their letters, one OS and one NS.
At what date did the first country start using the new calendar?
1582

This large collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system and how meteorites relate to asteroids and comets. New types of meteorites and rare meteorites have been found. Among these are pieces blasted off the Moon, and probably Mars, by impacts. These specimens, particularly ALH84001 discovered by ANSMET, are at the center of the controversy about possible evidence of microbial life on Mars. Because meteorites in space absorb and record cosmic radiation, the time elapsed since the meteorite hit the Earth can be determined from laboratory studies. The elapsed time since fall, or terrestrial residence age, of a meteorite represents more information that might be useful in environmental studies of Antarctic ice sheets.
About what nearby planet could the Antarctic meteorites hold data?
Mars

The Paris Region is France's leading region for economic activity, with a 2012 GDP of 624 billion (US$687 billion). In 2011, its GDP ranked second among the regions of Europe and its per-capita GDP was the 4th highest in Europe. While the Paris region's population accounted for 18.8 percent of metropolitan France in 2011, the Paris region's GDP accounted for 30 percent of metropolitan France's GDP. In 2015 it hosts the world headquarters of 29 of the 31 Fortune Global 500 companies located in France.
What percentage of Frances GDP is made up from the Paris Region's GDP?
30