Anything that happens globally can only be recorded at the Universal Time (UTC). As the Sun passes above the International Date Line (IDL), the old Universal day ends and the new day begins. But locally the old days may not have been completely off the earth. London GMT at that time is 12 midnight. But at the same time the last hour of the night in Makkah would be 3 am. An important point to note here is that the new day on earth will not begin until the day of Makkah is set. Similarly, the day will be set in the earth only after the dawn of the new day in Makkah. There is no need for more proof that the day begins at dawn. Similarly, the day in Makkah is the Universal day of Earth.
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