It is unclear exactly when Tibet’s anthem was first used, either while it was still a nominally independent country or first adopted by the government in exile after the takeover by China. The earliest report of an anthem (presumably this one) is from the period of 1949 to 1950 (when the Chinese assumed control of the country), introduced under reforms set in place for the country. Another report says that the anthem was presented to the Dali Lama in 1960, after he went into exile. (This could be simply a revision of either the music or lyrics introduced previously.)
Regardless of the adoption date, the melody is said to be based on a very old piece of Tibetan sacred music, and the lyrics by the Dali Lama’s tutor, Trijang Rinpoche. It has been used by Tibetans in exile ever since the introduction of the anthem (and, if the 1949 introduction date is correct, since the Chinese takeover in 1950), but is forbidden to be played within Chinese-controlled Tibet.