The clash at St Mary's had been due to take place on the Sunday in order to fulfil television commitments, but Chelsea's FA Cup quarter-final replay with Manchester United has forced the fixture to be changed.
"The game had already been moved once for the purposes of live Sky TV coverage – to Sunday, March 31 – however, the Premier League have deemed it acceptable to move the fixture once more," said the club's official website.
"The decision comes due to Chelsea and Manchester United needing a replay to determine the outcome of their FA Cup quarter-final tie, which will take place on Monday, April 1.
"The club is extremely disappointed that this decision has been taken, not least because of the significant inconvenience a second change to the fixture will cause our supporters. Tickets already purchased will still be valid for the rearranged date. Due to the move, this match will now not be broadcast live on TV."
Southampton currently sit 16th in the Premier League table.