Olympiad beginning on the opening of the Olympic Games for the summer sports. The first modern Olympiad began in 1896, the second in 1900, and so on (the 31st began in 2016: see the Olympic Charter). The ancient and modern Olympiads would have synchronised had there been a year zero between the Olympiad of 4 BC and the one of 4 AD. But as the Gregorian calendar goes directly from 1 BC to 1 AD, the ancient Olympic cycle now lags the modern cycle by one year. An ancient Olympiad was a period of four years grouped together, counting inclusively as
Chinese Chemistry Olympiad Chinese Chemistry Olympiad Chinese Chemistry Olympiad () is an annual academic competition held by Chinese Chemical Society. CAS changed its official Chinese name in February 2014, though its English translation remains the same. The first CChO was held in 1984, 16 years after IChO. The event has been held every year since then. China has selected excellent high school students to take part in IChO through the competition since 1987. It is considered to be the most difficult Chemistry exam throughout the world, the difficulty of Final round is much harder than IChO. The difficulty of the preliminary round is