Year 20X5

Year 20X5, in the Cosmic Calendar, was the year in which the Space Research Vessel Marina was attacked by the Space Pirates. The ship had been returning to Galactic Federation with samples of a newly discovered life-form before it was attacked. This life-form was called the Metroid, and it was discovered to have parasitic traits, including the ability to siphon the life energy of any living organism, leaving nothing but a brittle husk. The Space Pirates, desiring to use the Metroids as bioweapons, seized the creatures and made haste for their stronghold on planet Zebes, where they began to clone the Metroids by exposing them to beta rays. The Galactic Federation located the base, Tourian, but was unable to seize it. They sent in legendary Bounty Hunter Samus Aran to Zebes to destroy the Metroids, in what would be called her Zero Mission.

Metroid and Metroid: Zero Mission are set in 20X5. From there, the official timeline of the Metroid series is unknown. It is known that Metroid Prime takes place three years after Metroid: Zero Mission, but the placement of most of the following games is not clear. Further compounding this is the introduction of cycles in the Prime Series as an alternative method of measuring time.

Related manual quotes

 * Metroid manual:"It is now year 20X5 of the history of the cosmos, and something terrible has happened. Space pirates have attacked a deep-space research spaceship and seized a capsule containing an unknown life-form that had just been discovered on Planet SR388."
 * Metroid II: Return of Samus manual:"Samus' greatest achievement has been the destruction of the pirates' Metroid plans on the planet Zebes. In the year 20X5 of the cosmos, an unknown life-form was discovered on planet SR388 by a Galactic Federation deep-space research ship."
 * Metroid Fusion manual:"In Cosmic year 20X5, a Galactic Federation exploration vessel discovered an unknown organism on SR388. The hovering creature was a Metroid, an entity that exhibited frightening parasitic, energy-absorbing properties."
 * Metroid: Zero Mission manual:"In the year 20X5 of the Cosmic Calendar, a terrible incident occurred. The Space Pirates attacked a deep-space research vessel and seized capsules containing samples of an unknown species that had been discovered on planet SR388."
 * Metroid Prime Trilogy manual:"Cosmo Dating System, Year 20X5, Galactic Federation exploratory vessel was attacked and destroyed by Space Pirates which transporting an unknown life form that was captures[sic] on SR388. The Metroid was taken to a stronghold on the planet Zebes."