Let me bring the calculation of date that contradicts two major claims that we see in Bhutanese histories and many who speak following the same.
1. Let us see if Lam Lhapa who resisted Phajo was Nyo Lhanangpa.
Phajo was born in 1184 that is 20 years after the birth of Nyo Lhanangpa who was born in 1164. At the age of 7, that is in 1191 Phajo started his study under Nyingma tradition of buddhism, and at the age of 12, that is in 1196, he has met the Nyingma master Tharpalingpa from whom he got the name Dhondup Gyeltshen (some other has Tharpa Gyeltshen as the name given by Tharpalingpa).
By the time, Nyo Gyelwa Lhanangpa was already at his age of 32. Nyo Lhanagpa was recorded as arrived Bhutan in 1194 at the age of 30 and some histories say that he stayed in Bhutan for 11 years.
When Phajo was at 12, Nyo Lhanangpa has already passed his 2 years in Bhutan. Considering Nyo Lhanangpa as having stayed in Bhutan for 11 years in total, he returns back to Tibet either in late 1205 or early 1206.
Phajo according to the histories we find in Bhutan say, has arrived Bhutan at the age of 40 in 1224, at this period Nyo Lhanangpa turns his 60 the age at which he died.
And other dates state that Phajo arrived in 1222 and yet in another claims to have arrived in 1219. If Phajo arrived Bhutan in 1222 Nyo is at his 58 and if it was in 1219 Nyo is at his 55, he is at his later age already back to Tibet, where his final days were spent. Besides when his root guru, Lord Jigten Sumgon died in 1217 he was there in Tibet and there is no account to support his return after 1217 therefore, so many questions in the claims of the Bhutanese sholars. Since most of the scholars who identify Nyo Lhanangpa as the Lam Lhapa who fought with Lama Phajo are based on the biography of Phajo Drugom Zhigpo, it also poses a doubt on the authenticity and accuracy of the biography.
Does the dates support the claim of dongoen (blue stone) dzong as built by Nyo Lhanangpa?
Well as mentioned above, if Nyo lhanangpa has stayed in Bhutan for 11 years after he arrived in 1194, he returns back to Tibet either in 1205 or 1206. Dongoen (bluse stone) dzong according to the histories was built in 1216. How do we relate. Or do we now need to say that Nyo Lhanangpa actually stayed in Bhutan for 22 years? Or is it that the dongoen dzong was actually built by some other Lama a follower of Lhanangpa?
Histories however tell that Nyo Lhanangpa established at Chelkha soon he arrived in Bhutan, which means Chelkha dzong is the first ever dzong to have built in Bhutan. Dongoen dzong was ofcourse built by a Lhapa Lama and originally a monastery of Drikung untill it faced uniformation under Drukpa rule in the 17th century under Zhabdrung Rinpoche.