Except for Ketu, all the other 8 planets, or navgrahas, are
believed to have an influence during the 12 hours of day as per Hindu
astrology. These planets are called Yama Graha and have control from sunrise to
sunset.
The Yama Graha Planets are:
Sun (Ravi or Surya)
Moon (Chandra)
Mars (Mangal)
Mercury (Budha)
Jupiter (Guru)
Venus (Shukra)
Saturn (Shani)
Rahu
Rahu and Shani are considered inauspicious. The period
controlled by Rahu is known as Rahu Kalam. Each planet controls 90 minutes of a
day.