Losar is the Tibetan New Year, celebrated over 15 days, with the first three days the most important.
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.