General fact: 156 is the width in miles of a crater formed by an asteroid that may have hit Earth 1.8 billion years ago, according to researchers from the University of Toronto and Geological Survey of Canada.
Mathematical fact: 156 is the number of graphs with 6 vertices.
Trivia: 156 is the number of years that Hong Kong was under British colony rule.
Historical date: June 4th is the day in 1989 that Ali Khamenei is elected the new Supreme Leader of Islamic republic of Iran by the Assembly of Experts after the death of Ayatollah Ruhollah Khomeini.