1995 December – Initial planning
2004 August – GS Construction Consortium is picked
2005 October – Operating company is established
2007 July – Construction groundbreaking ceremony
2007 August – Full construction begins
2011 Summer – All track has been laid
2011 Fall – Signal work completion
2012 February to June- Testing of system
2012 June 29–30 – Free rides prior to official opening 
2012 July 1 – Revenue service begins
2014 December 6 – Joins metropolitan unity fare allowing transfers to other lines and buses.
Fares start from 1,350, with a flat 300 won extra charge if transferring from Line 1.
1995 December – Initial planning
2004 August – GS Construction Consortium is picked
2005 October – Operating company is established
2007 July – Construction groundbreaking ceremony
2007 August – Full construction begins
2011 Summer – All track has been laid
2011 Fall – Signal work completion
2012 February to June- Testing of system
2012 June 29–30 – Free rides prior to official opening 
2012 July 1 – Revenue service begins
2014 December 6 – Joins metropolitan unity fare allowing transfers to other lines and buses. Fares start from 1,350, with a flat 300 won extra charge if transferring from Line 1.
U Line