midnight
Oh , it took work and money -- the town was a wreck -- but it was possible to rebuild it entirely , especially because it was n't necessary to have all the details exact . `` There were the homes where even the brains had been utterly destroyed , and those are empty inside , and the cellars that need n't be too perfect , and the streets that hardly matter . And anyway , it only has to last for one day . The same day -- June 15th -- over and over again ; and if someone finds something a little wrong , somehow , the discovery wo n't have time to snowball , wreck the validity of the tests , because all errors are canceled out at midnight . '' The face tried to smile . `` That 's the dream , Mr. Burckhardt , that day of June 15th , because you never really lived it . It 's a present from Mr. Dorchin , a dream that he gives you and then takes back at the end of the day , when he has all his figures on how many of you responded to what variation of which appeal , and the maintenance crews go down the tunnel to go through the whole city , washing out the new dream with their little electronic drains , and then the dream starts all over again .