Final answer:
When it is noon in Greenwich, England, it is midnight at the international date line, with the date being different on each side of the line.
Step-by-step explanation:
The international date line is on the opposite side of the world from Greenwich, at the 180-degree meridian. When it is noon at the prime meridian in Greenwich, England, the time at the international date line depends on which side of the line you are on because it serves as the point where the date changes.
Traveling eastward across the international date line, you would subtract a day, and on the immediate west side, you would add a day. Given this rule, if it is noon at Greenwich (GMT or UTC+0), it is midnight (00:00) at the international date line, but the dates would be different. On the west side of the date line, it would be midnight going into the next day, while on the east side, it would be just after midnight on the previous day.