What are Njattuvelas? Periods of Sun. Daily motion of Sun = 360/365.25 and we get roughly 1 degree. SInce an Asterism or Constellation is 13 d 20 m, one Njattuvela’s duration = 13 days. Rohini Njattuvela started on 25th May at 08.39 AM, Makeeryam will start on 8 June at 06.32 AM and Thiruvathira on 22 Jun at 05.44 AM.