We’ve hit another significant marker in the countdown to polling day. There are now just 100 days to the election. Look out for a cavalcade of articles commenting on the significance of this date (guilty as charged) and using it as a hook to make all sorts of predictions about what is likely to happen between now and 7 May.

What makes the 100-day marker all the more potent is that we’ve never formally had it before. Though we’ve long known our parliaments can last no more than five years, this is the first time we’ve known precisely when a parliament is going to come to an end – and hence when we’ll hit the 100-day countdown.

Looking back over recent history, some rather pertinent events have taken place 100 days out from a general election.

For example, 100 days before the 2010 election, the UK officially came out of recession. GDP was estimated to have increased by 0.1% in the fourth quarter of 2009, bringing to an end the recession triggered by the economic crash of 2008. The date was 26 January, and Gordon Brown was in the middle of three days of talks with Taoiseach Brian Cowen to try and break the deadlock over devolution in Northern Ireland.

Brown’s government was also encouraging people to donate to the Haiti earthquake emergency fund (the island had been struck on 12 January). The Chilcot Inquiry into the Iraq War heard from Foreign Office lawyers Sir Michael Wood and Elizabeth Wilmshurst (the one official who resigned in the run-up to the conflict). In his diary, Chris Mullin records both the lawyers as saying:

They had advised Jack [Straw] that the war was illegal and that he had discounted their advice, saying it was too dogmatic. Perhaps Jack isn’t going to come so well out of this after all.

Five years on, we’re still waiting to find out.

100 days before the 2005 general election Tory leader Michael Howard had just made a speech on immigration, declaring: “People will face a clear choice at the next election: unlimited immigration under Mr Blair or limited, controlled immigration under the Conservatives.” In his diary Chris Mullin wrote: “As he well knows, this is a straight lie… Nevertheless, as Howard well knows, the poison is impossible to counter.” The date was 25 January. Both the EU and the UN opposed the Tories’ immigration plans, the Lib Dems had just pledged to increase maternity pay, and Labour had announced new plans aimed at helping first-time buyers.

If we spool back further to 2001, the 100-day countdown fell on 27 February. Dartmoor had just been closed to the public for the first time, following the nationwide outbreak of foot-and-mouth disease. The US ambassador to London rebuked the Tories for using his name in fundraising leaflets. Home secretary Jack Straw criticised lawyers for failing to fulfil what he called their social duty, and announced a 10-year plan to reform criminal justice. William Hague had just told the Tories to be ready for an election on 5 April. But as Tony Benn said in his diary:

The rumours at the moment are that the election will be postponed… Cattle are being slaughtered by the thousand; you see pictures of a dead cow being picked up by its leg by a crane and being dropped on to a pyre to burn. It really is a holocaust of animals.

In the event the election was postponed and didn’t take place until 7 June.

In 1997, the 100-day marker fell on 21 January. Gordon Brown, shadow chancellor, had just announced that a future Labour government would not raise either the basic or top rate of income tax. Alastair Campbell recorded the impact of this in his diary:

He got the kind of coverage – in terms of scale – you don’t normally see outside of party conferences… He had done it very effectively, bang in the middle of an interview with Jim Naughtie, he dropped it in. It was a big hit, one of those moments that you knew mattered.

In his diary, Tony Benn noted:

The combination of that with yesterday’s story about Nicola Horlick [a businesswoman who had just been sacked and had indicated her support for Labour] shows that we are a party that has adopted Tory policies. I have said it many times, but it is crystal-clear that that is what has happened.

Later that day, unbeknown to everyone, Tony Blair had dinner with Princess Diana. Campbell was also there: “At the dinner table, I three times felt a brush against my leg and couldn’t work out whether it was accident, deliberate or, on one occasion, one of the cats.”

All of the above events took place without almost anybody knowing an election was exactly 100 days away. It’s interesting to see some familiar topics rearing their head, however: the Chilcot Inquiry; immigration; help for first-time home buyers; pledges over tax. All four are almost certain to resurface in the 100 days left before this general election.