New Year's leave

What is so magical about 11pm on the 31st December 2021 (midnight in Brussels)? Having heard that there will be yet another shifting of the deadline in the Brexit negotiations, why not just keep negotiating until a deal is struck, even if that takes us into February, March or April next year? Why can’t the transition period continue until an agreement is reached? There is of course no natural, inescapable law which dictates the final deadline, unless one counts the government’s instinct for self-harm as immutable as gravity. There maybe something in that possibility. I can only interpret the pending deployment of four Royal Navy vessels to protect our precious fish in the event of no deal as one of the most absurd examples of gunboat diplomacy in recent history. Is this development meant to cow the French into submission (least of all French fisherfolk)?  I confess on my trips to the newsagent each morning I have not yet seen the Sun headlining with ‘UP YOURS, Macron’ but this surely is the level of subtlety which actually characterises our relationship with our ‘friends and partners’ (Johnson’ words) the EU countries. It makes me wonder what the leaders of those countries are saying behind Johnson’s back. And do they pity us for having chosen such a pitiable leader? The thing which doesn’t seem to be getting much attention at the moment is that even if the clock strikes 11am (GMT) on the 31st December, and there is no deal, trade negotiations will continue reflecting the fact the 46% of our trade is with the EU. I ask again: what is so magical about the 11pm on the 31st December?