593 B.C. The Mongols got tea from the Chinese and traded it across Asia. The Russians got tea in this way. Europeans first got into tea when the Portugese brought it back from China. In the 1700's tea had become an important item of trade. Both the British and Dutch bought tea in the Orient and sold it in Europe.
Tea is of course still very popular in England.
The British started planting tea in India in about 1818. Sri Lanka has been the second most important tea producer, but tea production there only started after the coffee rust wiped out coffee in 1880. Only the two or three youngest leaves are used for good quality tea. For green tea the leaves are dried fairly quickly to stop most enzyme activity. This modifies the tannins and polyphenols in the leaves.