calendar facts Selected as the most interesting among mathematics related questions in Mathematics quiz Augustus was born on 1 January 10BC. Which birthday did he celebrate at 1 January 10AD?19. There was no year number zero. There were only 1999 years between 1000BC and 1000AD.Created by: Gizem İsmailoğlumath facts » Which country started using 7 days in week?Babylon. The seven-day week has deep historical origins in the astrology of Ancient Near East, being approximately a quarter of a lunation. It was (independently) adopted by the Persian Empire, in Judaism and in Hellenistic astrology, and (via Greek transmission) in Gupta India and Tang China.Created by: $#O!@Bhistory facts » Which day was the last of the 20th century?31 Dec 2000. There was no year number zero. So, the first century started on 1 Jan 1. Similarly, 21th century started 1 Jan 2001.Created by: Jason Beagleytime facts » Typically, how many leap years are in a century?24. The Gregorian Calendar omits 3 leap days every 400 years, omitting February 29 in the 3 century years (integer multiples of 100) that are not also integer multiples of 400. For example, 1600 was a leap year, but 1700, 1800 and 1900 were not. Similarly, 2000 was a leap year, but 2100, 2200, and 2300 will not be.Created by: ex-terminatornumbers facts » Who introduced the Gregorian calendar?Pope Gregory XIII. Gregory XIII was pope during the period from 13 May 1572 until 10 April 1585. The Gregorian calendar, also called the Western Calendar, was introduced by him in 1582 with the Bull Inter Gravissimas. The gregorian calendar basically a refinement of the Julian calendar. The Gregorian reform modified the Julian calendar's scheme of leap years, changing the mean length of the calendar year from 365.25 days to 365.2425 days.Created by: Krzysztof Moskalpopes facts » How many months have 31 days in them?7. January, March, May, July, August, October and December.Created by: Kasiamathematics facts » Play mathematics quiz and see all the questions.