The new (unilateral) deadlines are:
1 October 2021 —Pre-notification and export health certificates (EHCs) required for animal-origin products. This includes goods that are only transiting through the UK, say from France to the Republic of Ireland. EHCs have been one of the biggest issues on GB-EU trade with minor errors leading to delayed shipments. They are time-consuming (and expensive) and must be completed by a vet, or other qualified person.
1 January 2022 —Physical checks to begin at the border, including on animal and plants products, along with requirements for safety and security declarations. Some products, such as chilled mincemeat and fresh sausages, will be completely banned from entering GB from the EU.
March 2022 —Physical checks to begin on live animals and low-risk plant products
From a cynical perspective, the benefit of these new deadlines for the government is that they kick the worst effects of Brexit still further down the road, delaying those empty supermarket shelves once dismissed as ‘Project Fear’. They want to get to the next election with as many voters as possible still not realising that Brexit was a bad idea and its worst impacts are yet to come. It’s a big reason why many speculate that Johnson will call an early general election.