What is the name of the festival in Tibetan Buddhism that is said to be the anniversary of Maitreya Buddha's birth?

Welcoming Jampa Buddha Festival is also called the ceremony of welcoming Maitreya Buddha to circumambulate the monastery

Every year on the 15th day of the 2nd month of the Tibetan lunar calendar, headed by a representative of the bodhisattva Xiwang Sangpo and a senior monk, Living Buddha Paldangshi, all the monks dressed in gorgeous vestments, holding countless tributes such as precious umbrellas, treasure blocks, flying streamers and other kinds of offerings, neatly performing the ceremony of bathing and enlightenment on the four sides of the temple compound, especially in the center of the front of the temple, where the satin statue of Maitreya Buddha is hung and a grand ceremony is performed to welcome the portrait of Buddha Sakyamuni and the image of Maitreya Buddha, and to welcome the Buddha's portrait. In particular, the satin statue of Maitreya Buddha was hung in the center in front of the temple and a grand ceremony of bathing and opening of the light was performed to welcome the portraits of Buddha Shakyamuni and Maitreya Buddha. At this time, tens of thousands of people come from all directions, because this is a grand festival to open the door of karma for all beings, including the gods, to obtain the right to a victorious life and permanent peace and happiness, and it is the best time for all beings to be blessed.

Jampa Buddha, also known as Maitreya Buddha, is known as the future Buddha in Buddhism. Maitreya is a shortened translation of the Sanskrit word Maitreya, which means "Mercy". It is said that this Buddha always has a heart of great compassion. The Amitabha Sutra says: "Or Maitreya, this is Tzu. Because he practiced compassion more, more into the compassionate mind, so the word Ci's, cultivating compassion is the most victorious, the name can not win." According to the suttas, Shakyamuni Buddha said that his disciple, Ayitto (i.e., Noble Victor), would cultivate to become Maitreya Buddha. Born into a Brahmin family in the ancient Indian country of Paranay, Ayitto later followed Sakyamuni Buddha and became a disciple of the Buddha. He passed away before Sakyamuni passed into nirvana. Tibetan temples generally offer Maitreya Buddha.

For the origin of the festival, I would like to find the source, but turned over many books or no definitive answer. Just from a booklet introducing Qiangbaling Monastery, I found some records: In the "Wave Ru Empowerment Sutra", it says: "These effigies have become like me because they have been empowered by all the Buddhas of the three times. Moreover, in this place, carriages will pull my gigantic statue and offer it in a castle called the Good One as a place of great offerings, and all the great merchants will gather together from all directions, and disasters will also be eliminated." It was also foretold in the Vinaya Sutta Shakya Matters that the effigy of the Buddha would circle the city. As predicted above, the tradition of welcoming Maitreya Buddha was started by the three-time Dharma King Tsongkhapa after the Great Puja in Lhasa, and it has gradually become popular.