Moodami means the darkness in Sanskrit. When the grahas (planets) Brihaspati or Guru (Jupiter) and Shukra (Venus) near the Sun (Surya), the Moodami occurs. The planet which nears the Sun loses its energy and power. The darkness occurs in the time of planetary motion.
The two Navagrahas, Brihaspati and Shukra are good and prosperous planets. The position of Grahas and their energy are important to accomplish any work.
During Guru Moudyami and Shukra Moudyami we should avoid functions, celebrations and inaugurations.