How is the Day of Arafah fasted, given the time difference between countries and the time of the pilgrims' standing at Arafah?

Fasting on the Day of Arafah is determined for each country's inhabitants according to their local dawn and sunset. Fasting on this day expiates the sins of two years, as the Prophet, peace and blessings be upon him, said: "Fasting on the Day of Arafah, I hope from Allah that it will expiate the sins of the year before it and the year after it."