As well as being the day that Gordon Brown finally announced that an election would be held on 6 May (he accurately described it as "the least well-kept secret of recent years") today is also the day that the new 50p tax rate comes into force.
It's not a bad day for this to happen. The new top rate of tax, like the one-off tax on bank bonuses, is one of the most popular policies Labour has adopted in recent years. A YouGov poll found that 68 per cent of voters support the introduction of the 50p rate.
With the economy defining this election like no other, the parties' tax pledges will come under even more scrutiny than normal. Cabinet ministers, led by Ed Balls, have challenged the Tories to admit that they will need to raise VAT to plug the deficit.
George Osborne has insisted that he has "no plans" to increase VAT, but this is clearly a non-denial denial. As Sunder Katwala reminds us, the former Tory chancellor Geoffrey Howe similarly declared that "we have absolutely no intention of doubling VAT" during the 1979 campaign, and then did just that. Later, it was the Major government that raised VAT by 2.5 per cent to its current level of 17.5 per cent.
But until Labour issues a copper-bottomed guarantee that it won't do the same, the party's attack on the Tories won't win over any voters.
The Labour manifesto, a preview of which appears in today's Guardian, should contain such a pledge. A promise not to raise the most regressive tax of all would emphasise Labour's commitment to fair taxation and would hand Brown one of the "dividing lines" he so craves.
The Tories' promise to reverse part of the government's planned National Insurance increase kick-started their faltering campaign. A promise not to raise VAT could do the same for Labour.