The State Opening of Parliament by the Queen is to take place on June 21, after it was delayed by the inconclusive outcome of last week's General Election.
The new date for the event, which will feature the Queen's Speech setting out the Government's legislative programme for the coming year, is two days after it was originally scheduled to take place.
It comes as negotiations continue between Theresa May's Conservatives and the Democratic Unionist Party (DUP) over a deal under which the Northern Irish party could prop up a minority Tory administration.
Confirming the date, the Leader of the Commons Andrea Leadsom, said: "The Government has agreed with Buckingham Palace that the State Opening of Parliament will take place on 21 June 2017."
The State Opening was initially scheduled for June 19 - the same date when Brexit negotiations were due to begin in Brussels.
It is not yet clear whether the EU withdrawal talks will go ahead on that day, although Brexit Secretary David Davis has said they will start "next week".