Gedong Festival, held at most Tibetan Temples at the end of the Tibetan year.
Tibetans in Yunnan have their own festivals, held according to the Tibetan Calendar.
The Tibetan Calendar is extremely complex, with many missing and duplicated months and days. The calculations here follow the paper by Swante Janson https://www.yunnanexplorer.com/bibliography/publication/jansonswante/ Be careful and check the exact dates of the festivals before setting out.
Main day for the masked dances is the evening of the 11th lunar month in the Tibetan Calendar. It is said that the dances take place on the 26th and the 30th day of the months. Not sure if there are any activities between.