How is the Day of Judgment determined if Friday, the 10th of Muharram, varies in time between countries due to time differences?

Everyone who sets a date for the Day of Judgment is a liar, for its knowledge is with Allah alone. When the Day of Judgment comes, the world's system will change, and no one knows whether America will exist then, for Allah is capable of destroying any nations He wills before the Day of Judgment.