Key dates.

April 2 - seven-cornered party leaders' TV debate.

April 7 - STV debate with four main Scottish party leaders.

April 8 - BBC Scotland debate with four main Scottish party leaders plus Scottish Greens and Ukip.

April 9 - deadline for candidates registering their intention to stand.

April 13 - UK party manifestos expected to be launched during this week.

April 16 - "challengers' TV debate", featuring opposition UK party leaders.

April 20 - deadline for people to register to vote.

April 21 - deadline for people applying for a postal vote.

April 28 - deadline for applying for a proxy vote.

April 30 - BBC Question Time special, featuring Cameron, Clegg and Miliband.

May 3 - second BBC Scotland TV debate with leaders of four main Scottish parties.

May 7 - polling day.

May 8 - the result.

May 18 - new parliament summoned.