Today's History Channel calendar is very relevant to TG2 fans -

"Eratosthenes, a Greek academic, was the founding father of geography. He invented the system of latitude and longitude and, on this day [June 19th] in 240 BC, offered up the first measure of the planet Earth. Modern mathematicians approximate that his calculations reflected a size of 25,000 miles in circumference, only 98 miles more than the modern value of 24,902 miles."