Following from the previous Wiki, the return to a 2 year qualifying period for unfair dismissal claims commences April 6th 2012 - BUT note that the clock is zeroed at April 6th, so someone who commenced employment (say) May 1st 2011 will only need a one year qualifying period.

The above of course does not include dismissals where there is no qualifying period currently - so no change in some circumstances (ERA 1996)