Scottish referendum: Glasgow No supporters celebrate with cheers at dawn
Four thirty in the morning is the time even the liveliest parties tend to wind down.
The guests - some of them looking the worse for wear - begin to leave; the plates and champagne bottles are cleared away; the party balloons begin to shrink and sag.
But at the Marriott Hotel in Glasgow, 04:40 BST was the time people started to stand up, fill (or re-fill) their glasses and turn their attention to the giant TV screens on the wall.
Crammed into a stifling conference room, two hundred or more "No" campaigners watched the coverage and saw that the referendum was going their way.
These were the people who'd manned the street stalls and the phone banks; they'd walked the pavements, handed out leaflets and knocked on doors for more than two years. Now they were going to party.
Renfrewshire, East Lothian, Stirling, Aberdeen. As each new "No" majority came in, the cheers got louder, the room got hotter.
A couple of weeks ago, it looked as though this might not happen. The polls suggested the "Yes" campaign might pull off an historic and irreversible win.
In the Marriott many people said they were always quietly confident of victory. They hadn't been as visible or vocal as the "Yes" campaign but they felt their arguments were stronger.
"I think there was a big silent No vote," said one man in his 20s. "People were fundamentally not swayed by emotion or big speeches... it was won by people who were concerned for their pension, the NHS and the overall welfare not just of Scotland but the wider United Kingdom."
As more results came in some polite hugs turned to big, long group hugs.
A woman released her grip on a friend to tell me: "We're proud Scots but we're proud to be British as well... it's wonderful, wonderful, wonderful to be part of all of this and to celebrate!"
As if to provide a fanfare for the campaign chairman, Alistair Darling, there was a chorus of "We Love Scotland! We love Scotland! Scotland says No!"
Saltires were waved and flapped. And then he walked in and climbed onto the stage.
Mr Darling had not been partying and in his crisp blue suit looked slightly out of place in a roomful of referendum revellers.
"We have chosen unity over division" he told them. "The silent have spoken".
As dawn broke, there were tears as they said their goodbyes. They'd done it. They'd saved the Union. The party was over.