... against either Manchester United or Chelsea will take place on Sunday, April 14, with a 4pm kick-off.
Having booked their place in the Europa League quarter-finals, Chelsea now know they face a trip to Russia to take on Rubin Kazan on April 11.
And with the FA needing to arrange the semi-final dates before the outcome of Chelsea's quarter-final replay with United has been determined, a Sunday fixture was automatic.
It means the tournament's remaining npower Championship side, Millwall, will aim to reach the final on Saturday, April 13, when they tackle Wigan, who have never reached this stage before.
Both matches will be played at Wembley.
It has also been confirmed that Millwall and Manchester City have been allocated the west end of the stadium and will receive 31,514 tickets.
Wigan and the other semi-finalists will get 31,863 tickets.