The Chernobyl nuclear disaster happened during the night of 25–26 April 1986, with the catastrophic explosion in Reactor 4 occurring at about 01:23 on 26 April 1986.

Date and time

  • The reactor accident took place at the Chernobyl Nuclear Power Plant, then in the Ukrainian Soviet Socialist Republic (USSR), now in Ukraine.
  • The critical explosions that destroyed Reactor 4 occurred around 1:23 a.m. on Saturday, 26 April 1986.

Short context

  • The event is widely regarded as the worst disaster in the history of nuclear power generation, due to the massive release of radioactive material and long‑term contamination.
  • Evacuations of nearby Pripyat and surrounding areas began later on 27 April 1986, about 36 hours after the initial explosion.

TL;DR: Chernobyl “was” in the sense of the main reactor explosion happening on 26 April 1986, just after 1:23 a.m., at the Chernobyl Nuclear Power Plant in the former USSR.

Information gathered from public forums or data available on the internet and portrayed here.