Because his resurrection went wrong, and it was 2009.
No, it was 2010. The Whoniverse is set one year ahead of current time due to the events in "Aliens of London" where Rose had been "missing" for 12 months.
It was since retconned so the Whoniverse is in sync with real time once again
Indeed, it was 2009, as confirmed in commenterary. And series 5 takes place throghout 2010, as confirmed by leaked aidio. The 2009 specials took place in the same year as series 4, retconing the year skip.