Timeline of Events

Two Thousand Years ago: Due to tectonic shift the continents have converged once again and created three new continents made up of the 7 previous.
Nine Years ago: The Incident Occurs releasing Daiya Syndrome into the atmosphere and it stains the sky red, effecting the climate and weather patterns.
*Yuki is born Ten days before the incident.
Three Years ago: Reconstruction of City of Daiya Chiri completed.
Present Day: 
*Seito accidentally commandeers Unit Zero and becomes a wanted man. 
*Events of the canon start.