The Chernobyl disaster was a catastrophic nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in the town of Pripyat, in Ukraine , which was under the direct jurisdiction of the central authorities of the Soviet Union. An explosion and fire released large quantities of radioactive particles into the atmosphere, which spread over much of the western USSR and Europe.
Encyclopedic entry. The date line, also called the International Date Line, is a boundary from which each calendar day starts. Areas to the west of the date line are one calendar day ahead of areas to the east.