It was, according Scottish Nationalists, "the day Westminster lost Scotland".
A defining moment in the constitutional debate.
From that day on everything would be changed, changed utterly.
They are referring to the vote taken in the House of Commons a week ago - after some 15 minutes of debate - to pass the part of the UK government's Brexit bill that deals with devolution.
You'll remember that after he protested against this at Prime Minister's questions two days later the SNP leader in the Commons, Ian Blackford, was suspended for a day and led a walk-out of his MPs.
With the backing of First Minister Nicola Sturgeon, Nationalists could not accept the Westminster "power grab" on powers coming back from the EU which they say should lie automatically with Holyrood.
Since then the SNP has promised (threatened, their opponents would say) to do whatever it can to frustrate the workings of Westminster, arguing that the UK parliament no longer speaks for Scotland.
In this the politician they seek to emulate is Irish home rule campaigner Charles Stewart Parnell - whose statue stands just outside the SNP leader's office in Westminster - who was a master of disruptive, but legitimate, parliamentary procedure.
We shall see how far down the Parnellite route the SNP go, but many would agree they are justified in doing so, as that both Scottish Secretary David Mundell and Scottish Tory leader Ruth Davidson promised more substantial Commons debate on devolution and Brexit - debate which failed to materialise.
But what is now perhaps more important than parliamentary disruption - where there is a danger the public see it as politicians playing games - is whether the mood in Scotland is as the SNP say it is?
In what was a particularly heated emergency debate in the Commons last night SNP leader Ian Blackford suggested there would be the same reaction in Scotland to the 'power grab' as there was to "the poll tax under Thatcher".
Others of his MP colleagues said the reaction they were getting from their constituents compared to the opposition there had been to the decision to go to war in Iraq made by Tony Blair.
In his speech Mr Blackford repeatedly attacked Mr Mundell's credibility as Secretary of State, calling him "yellow", saying he had come "crawling" to the Commons, and making deeply disparaging comparisons with his predecessors.
Whether or not that was edifying is a matter of personal political taste, what was arguably more significant was Mr Blackford's rhetoric which reminded this writer of SNP conferences before the party was the substantial political force it has become.
Mr Blackford said Mr Mundell saw Scotland as "subservient" to Westminster. The Secretary of State has "stabbed the Scottish parliament and the Scottish people in the back".
The UK government has used "the majority they have from England to take power back from the people of Scotland".
The Scottish parliament was being "emasculated by an anti-Scottish Tory government here in London".
Scotland had been relegated from a region to a nation with a "subordinate relationship" to Westminster.
The power grab was a "dark day for Scotland" and the only service Mr Mundell had done was to "help strengthen the case for Scottish independence".
Now it should be said that Mr Backford's MP colleagues sitting around him loved this rhetoric and stood up to praise him, but I certainly cannot remember Nicola Sturgeon striking such a tone a speech, or using similar language - though I am sure I will be corrected if I am wrong about that.
The only reply Mr Blackford got from Mr Mundell, who was not the UK government's chosen speaker in the debate, was that it was "not worthy of a response" because of its tone.
In a brief intervention the Scottish Secretary, and south of Scotland MP, said Mr Blackford had called for a respectful debate but undermined his case by the personal nature of his comments.
"This may be a performance for his colleagues, it may be a performance for his core voters, it doesn't impress Scotland, " Mr Mundell added before sitting down to listen to cabinet minister David Liddington lead for the UK government.
However, in making this short point Mr Mundell actually raised the issue at the heart of this increasingly fractious and bitter debate: will the SNP case resonate with the voters, or will it not?
To try to get an answer to that I went to the experts. Does the ramping up of the rhetoric on the 'power grab' by the SNP give the party what political operatives call 'traction' with voters?
Professor Sir John Curtice, who has studied attitudes to the constitution in Scotland over many years, said:
Prof Curtice, of Strathclyde University, added:
Pollster Mark Diffley believes the constitutional issue of the power grab itself will not move voters. But he does think polling showing voters trust the Scottish government more than Westminster could be significant.
Mr Diffley, formerly of Ipsos MORI who recently set up his own consultancy business, said:
Agreement then, broadly speaking, from the experts.
So, if the SNP's rhetoric can cut through to the public, if they can make it resonate, if they do get 'traction' then they will benefit and we will, as they warn, be heading for a constitutional crisis or a poll tax Mark II.
If, on the other hand, Mr Mundell is right and their tactic "doesn't impress Scotland", then the crisis will be averted, and voters will continue to go about their business unmoved even by the fiery rhetoric and fevered constitutional clashes between Nationalist and Tory.
Naturally, both sides think they are right. They can't both be.