Article: In 1661 another Jesuit, Johann Grueber, crossed Tibet from Sining to Lhasa (where he spent a month), before heading on to Nepal. He was followed by others who actually built a church in Lhasa. These included the Jesuit Father Ippolito Desideri, 1716–1721, who gained a deep knowledge of Tibetan culture, language and Buddhism, and various Capuchins in 1707–1711, 1716–1733 and 1741–1745, Christianity was used by some Tibetan monarchs and their courts and the Karmapa sect lamas to counterbalance the influence of the Gelugpa sect in the 17th century until in 1745 when all the missionaries were expelled at the lama's insistence.

Question: When did Johann Grueber cross Tibet on the way to Nepal?
1661