Today, the 21 October 2015, is the destination for Marty McFly and his eccentric scientist travelling companion Doc Brown in the Back to the Future sequel.
And there was not a chance in hell that the Prime Minister was going to ignore the opportunity to throw in a gag about it in the Commons.
When asked by Tory MP Iain Stewart about nuclear deterrents, Cameron said it was “absolutely right” that Britain maintain Trident.
Responding to a question about whether Corbyn was wrong to want Britain to get rid of its nuclear weapons, Cameron replied: "Today we are celebrating that great film Back to the Future, I am not surprised that many people sitting behind him say he should get in his Delorean and go back to 1985 and stay there."
The Conservative Party, and some Labour MPs, view the Labour leader's views as more suited to the 1980s than the present day.
But Corbyn effectively accused Cameron himself of going back to a Thatcherite future, to a time when the 'working poor' didn't have tax credits to help them make ends meet.
He repeatedly attacked the Prime Minister over his planned cuts to tax credits that will leave many thousands of pounds worse off, pointing out that it was 'all very strange' that he had promised not to cut them during the general election campaign.
In turn, Cameron dismissed tax credits as a '20-year experiment' that had failed to end child poverty and said it was 'quite strange' that Labour's deputy leader Tom Watson had failed to vote against the cuts plan on Tuesday night.
People tweeting about PMQs were less than impressed by the joke, saying the Tory leader had "ruined" this historic day.