Background: Dion Dublin (born 22 April 1969) is an English former footballer and television presenter. Born in Leicester and of Nigerian descent, he was capped four times for England. Dublin started his career as a centre-back with Norwich City, but made his name at Cambridge United as a centre-forward. He had spells with Norwich City, Cambridge United, Manchester United, Coventry City, Millwall, Aston Villa, Leicester City and Celtic.
Context: On 20 September 2006, Norwich City announced that Dublin had joined them until the end of the 2006-07 season. It marked a return, almost 20 years after leaving, for Dublin to the club where he began his career. He made his debut on 23 September 2006 when he came on as substitute against Plymouth Argyle. He scored his first competitive goal in Norwich City colours in a 3-3 draw against Queens Park Rangers on 14 October 2006 at Loftus Road. Steve Wilson cited Dublin as the main inspiration behind Norwich's 4-1 FA Cup 3rd Round win at Tamworth, in which the striker scored two goals and set up numerous chances for other teammates.  Dublin was an important figure in Norwich securing safety from relegation to League One and the supporters recognised his contribution by voting him in second place in the Norwich City player of the year award, and on 23 May 2007 he ended speculation about his future by signing a new one-year contract at Norwich, keeping him at the club until the end of the 2007-08 season. On 2 September 2007, Dublin, whilst a pundit on the Aston Villa v Chelsea game, said that this season would be his last as a footballer, citing the fact that his 'bones have started to talk to him' as the reason, meaning that he did not think his body can handle another season.  During Spring 2008, Dublin was approached by Jimmy Quinn, then manager of Cambridge United, about joining his old club for the 2008-09 season. However, the player would not change his mind about retiring. He was voted the club's Player of the Year and awarded the Barry Butler trophy on 26 April 2008 in his final season as a footballer, at his penultimate game, and on his final appearance at Carrow Road. Dublin played his final game on 4 May 2008, featuring in Norwich's 4-1 loss to Sheffield Wednesday in front of 36,208 fans at Hillsborough - the highest Championship attendance that season. When he was taken off in the 66th minute, Dublin received a standing ovation from both sets of supporters, players and referee Mark Clattenburg.
Question: When did Dublin join Norwich city for his second spell ?. Whats the answer?
On 20 September 2006, Norwich City announced that Dublin had joined them until the end of the 2006-07 season.