Copenhagen - striking accord?
Arguably, it's a deadline that isn't a deadline for an accord that isn't an accord.
"It" is - or was - the 31 January target date by which governments were supposed to tell the UN climate convention (UNFCCC) secretariat what pledges they are prepared to make on curbing greenhouse gas emissions.
The date stems from the Copenhagen Accord - the agreement cobbled together at the end of December's UN climate summit in the Danish capital.
It received less than universal support at the summit, and since then UNFCCC executive secretary Yvo de Boer has indicated that 31 January isn't a deadline anyway.
So does who sends in what really matter?
UK Prime Minister Gordon Brown believes it does; and in an open letter, he's just set out some of the reasons why.
If countries that indicated support for the accord at the summit send their submissions in, he writes:
"For the first time, the world will see, collected together, strong mitigation commitments by countries representing more than 80% of global emissions.
"If those commitments are then implemented to their maximum potential, they could lead to emissions peaking by around 2020 or before, representing the crucial first step towards the level of reductions required to hold global temperature increases to under 2C."
The UNFCCC hasn't released details of who has sent in what - they're expected to do so during Monday or Tuesday - but a number of key players have said they would make submissions, including the US, the EU and the Basic group of Brazil, China, India and South Africa. (NB: SEE UPDATE BELOW)
An argument made in some quarters as to why it matters is that the number of countries sending in submissions will indicate the extent of support for the Copenhagen Accord.
Implicit in this argument is a belief that the accord might be instrumental in holding countries to their pledges. It also ties in with a belief that the accord can be the basis for the bigger, more legally framed treaty that the EU and a number of developing countries say they want to secure at this year's UN conference in Mexico.
Do these views hold water, though? One reason why they might not is that the accord didn't bring any commitments from any countries above and beyond what they had pledged in the run-up to Copenhagen.
Compare countries' statements of intent as of November, say, with what they have sent to the UNFCCC and my guess is that you will not see a jot of difference. Some were going to do what they pledged anyway, unilaterally, accord or no accord.
And some, such as the EU, have indicated they'll now adopt targets at the weak end of the ranges they'd proposed - an action confirming that the accord is regarded as lacking in ambition.
And as I've asked before on this blog: given the way Copenhagen turned out, what basis does anyone have for believing that there is appetite among all significant parties for a stronger agreement with at least a whiff of legal obligation?
The agenda in those final hours of the summit was set and driven by the Basic bloc, who are most insistent that their own pledges must be regarded as voluntary. This view has been given additional emphasis by a report in the Danish press that the Basic countries had agreed how far they would go a week before the Copenhagen summit convened, during a meeting on 28 November in Beijing.
The bloc now plans to hold quarterly ministerial meetings on climate change.
So here's a provocative question: given the outcome of Copenhagen, and given the strength of the sinews that these powerfully developing nations are beginning to flex on a more regular basis in all sorts of arenas - see our coverage of the Davos economic forum last week - are these regular four-nation meetings now the most important events for deciding where the world is going on climate change?
UPDATE: The UNFCCC has now released details of submissions so far received. Top stats are: 55 countries, accounting for 78% of global emissions from energy use.
According to Yvo de Boer:
"The commitment to confront climate change at the highest level is beyond doubt."
See our news story here.