Whenever the following year sign come in play and the Mewa is 2 (nigna) than the year is inauspicious known as Lonang (Black year) in Bhutanese.
The back year are of two categories, Lonag Chewa (Worst black year) and Lonag Chungwa (bad black year).
If Mewa 2 falls with Tiger, Pig and Monkey than the year is Lonag Chewa.
If Mewa 2 falls with Ox, Sheep, Dog and Dragon than it is Lonag Chungwa.
During black year, no important work is undertaken viz. construction of houses, buying and selling of property, marriage etc.
However, starting Thendrel can be done before Lonang sets in and the work can be continued in the black year.
Please note that if Mewa 2 falls with other animal signs other than the above signs than it is not considered a black year.