The UK will leave the EU at 11pm on Friday - 1,317 days after the vote for Brexit.
Boris Johnson will hold a Cabinet meeting in the north before a night-time TV address from Downing Street, festooned with a projected countdown clock and a light show.
3million special 50p coins will enter circulation, Union flags will hand in Parliament Square and outside Buckingham Palace - and despite efforts to, Big Ben won't bong.
No one can deny it's a historic moment. Britain is the first nation ever to leave. But what about beyond the pomp and ceremony? What will actually change for you, your loved ones and the country?
Here's a guide to what our leaving the EU on Friday means.
What happens at 11pm on Friday 31 January?
This is the legal moment that the UK becomes the first nation ever to leave the European Union - after three failed exit dates of March 29, April 12 and October 31 last year.
It's at 11pm because that's midnight Brussels time.
At this instant, the EU Withdrawal Agreement Act, passed by Parliament last week, will take effect.
It will translate thousands of EU regulations from recent decades into UK law, to ensure we don't fall into a legal black hole.
It will also make legal the 'transition period', continuing EU rules until December 31, and begin £39bn in 'divorce bill' payments to the EU which stretch for several years.
Meanwhile, No10 will mark the moment with a speech by Boris Johnson, a light show and a countdown clock projected onto the black bricks of 10 Downing Street.
Just down the road in Parliament Square, Nigel Farage and Tory Brexiteers will hold a rally.
What will actually change?
From 11pm the UK is legally out of the EU and can no longer "cancel" Brexit by revoking Article 50. UK citizens will cease to be citizens of the EU.
If the UK wants to rejoin the EU, it has to do so under Article 49 of the Lisbon Treaty, a lengthy process that needs the approval of all 27 states.
Yet nothing much will change in your day-to-day life for 11 months, until 31 December 2020. That's because we are in a 'transition period' and continue to follow EU rules until then.
The Brexit deal says the transition period can be extended by two years. But the government passed a law banning this.
How much things change after 31 December depends on whether we get a trade deal with the EU.
If we do, there will be a new set of rules from 1 January 2021. If not, we could crash out on 'WTO terms' - the basic rules that slap high tariffs and restrictions on trade. There's more detail below on the things that might change in January 2021.
But there are still some things that will definitely change from Friday.
The Brexit Department will be abolished and a new Taskforce Europe Team within No10 will lead the UK's trade talks - headed by the PM's chief Europe adviser David Frost.
Brexit Secretary Stephen Barclay will lose his Cabinet job, though he could be given another one elsewhere.
Blue passports will start being issued to all new applications, instead of the burgundy ones, from "mid 2020" and have already lost their European Union branding. Your old passport remains valid though, as long as it's in date.
The economy will have some security thanks to the deal, but isn't expected to rocket while speculation continues in the transition period.
Some analysis has claimed house prices will rise as buyers move after years of uncertainty, but sellers are also coming on to the market too so the verdict is far from certain.
These things won't change yet - but you should watch out
Travel firms are insisting everything will remain the same for UK holidaymakers in the EU after January 31.
That is because there will be no restrictions on travel to the EU until at least January 2021.
Queues of lorries at ports aren't expected either because there will be no extra checks. But again, these could spring up in January 2021 - especially if there is no trade deal.
The shape of the future relationship, trading checks or any travel restrictions is not yet established, and will be part of trade talks over the next 11 months.
Passports and visas
Brits will not need a visa to travel to the EU after January 31. You can keep using EU passport gates at airports.
UK government guidance says you won't need a visa from 1 January 2021 either - if you're a tourist.
But you will have a limited stay of up to 90 days in any 180-day period, and you may need a visa or permit to stay for longer. You may also need to show a return ticket, show you have enough money for your stay, and stop using EU passport lanes at European borders.
From 2021, Brits must also have at least six months left on their passports if going to the EU.
Your passport must also be no more than 10 years old, even if it has time left, from 1 January 2021.
After January 31, a UK driving licence is still the only thing visitors need to get behind the wheel in the EU.
But after 1 January 2021 you may need to get an International Driving Permit. There are three types - make sure you get the right one for the right country. A full list is here.
The £5.50 documents were once a niche bit of paperwork but 7million a year are expected to be handed out.
After 1 January 2021 you also need to apply for a 'green card' to prove you have the right car insurance (if using your own car). Allow a month to get this from your insurance firm.
You also need a GB bumper sticker.
Bringing pets abroad
Pet owners can carry own bringing their beloved animals to the EU on 'pet passports' until December.
But they must prepare four months in advance if they are planning a holiday on or after 1 January 2021.
Current advice for after January 2021 is the animal must have a rabies vaccination, followed by a blood test at least 30 days later, to prove the vaccination worked.
Pet owners must then wait at least three months before visiting the vet to obtain a health certificate.
But to add an extra layer of red tape, this cannot be done more than 10 days before the date the holiday starts. So you need to get your timing right.
Healthcare in the EU
Nothing changes from 11pm on Friday - but you should start preparing for 2021.
From the end of 2020, the European Health Insurance Card (EHIC), which gives Brits access to EU healthcare in an emergency, will no longer work.
After that there will not be one EU-wide regime on healthcare. Instead it is up to the UK to strike "reciprocal" health cover with individual states - a sort of 'we'll fund your people if you fund ours' system.
Back last year the UK and Spain struck an agreement to continue health cover until the end of 2020 if there was no deal. One might expect a pact after that too, but for other countries it's less certain.
Because of this, travellers from the UK to EU are being told to ensure they have adequate insurance for the full duration of their trip in 2020 and beyond.
For EU migrants to the UK, if there is no reciprocal agreement, there is a £400-a-year charge to use the health service.
EU citizens can continue arriving freely in the UK to live and work until 31 December 2020.
But they must apply by June 2021 for "settled status", which gives them the right to stay in the UK.
Those who haven't lived in the UK for five continuous years have to apply twice - first for "pre-settled status", then again for settled status when they hit the five-year mark.
After 1 January 2021, new EU citizens who want to come to the UK will be subject to a points-based immigration system. They will have to prove their skills and probably earn a minimum salary.
Again, there will be no change from January 31 - but things could change from 1 January 2021.
Upon leaving the EU, there will no longer be guaranteed free mobile phone roaming for UK customers on the Continent as the issue will be left to the market.
You're advised to check with your phone operator if travelling after 1 January 2021.
UK citizens can continue arriving freely in EU countries to live and work until 31 December 2020.
But to stay after that date ex-pats will need to apply for a residency status. The exact system varies by country but the UK government claims it will be "short, simple and either free of charge, or cost no more than applying for a similar document, for example a national identity card or passport."
Guides for expats in each country will appear here as they are thrashed out.
Trade with Northern Ireland
There will be no change after January 31, but there will be major changes after 1 January 2021.
The Withdrawal Agreement avoids putting up a hard border along the 310-mile line between Northern Ireland and the Republic.
But EU chiefs say checks will be "indispensable" on goods travelling between Britain and Northern Ireland.
The Freight Transport Association warned that means filling out 42 data fields for goods going west to Belfast - and 29 for goods going east back to Great Britain.
Again, there will be no change from January 31. But from 2021 the UK government will be free to depart from EU workers' rights laws if it wants.
Boris Johnson rejected pleas to tack to future laws protecting workers, instead opting for an independent approach.