The Sahabah (radi Allahu anhum) asked Rasul Allah (sal Allahu alaihi wa sallam) about the Dajjal, “O Messenger of Allah, how long will he stay on earth?” He replied, “Forty days; a day like a year, a day like a month, a day like a week, and the rest of the days like your days.” [Sahih Muslim]
Interpretations of the Hadith by Sheikh Imran N. Hosein
He says that the first three days that are mentioned are metaphorical. He further explains that the first day means the British Rule perhaps starting in 13th century till they lost their power somewhere in the 20th century.
Second day that's equal to one month means the American Rule starting right after the fall of the Great British Empire till they too will fall somewhere soon into the future.
Third day that is equal to a week means the day America falls and a new super power rises, most probably Israel.
After the rise and fall of this new super power, Dajal will appear in physical form and be killed by Prophet Isa peace be upon him.
