Shravan Maas or the month of Sawan is the fifth month of the Lunar Calendar. As per the Hindu scriptures and Vedas, Shravan maas or the month of sawan is considered as highly auspicious month. Vedas describe Sawan as the month as ‘Nabhas’. ‘Shravan Purnima’ -the full moon day in the month of Sawan coincides with the birth star of Lord Vishnu, the Shravana Nakshatra.
Rahu will enter Virgo from Libra after 18 months and Ketu will enter Pisces from Aries after 18 Months, as per their mean position calculation. Rahu and Ketu are not planets, but basically 2 astronomical points in the zodiac always opposite to each other and 180 degrees apart. This is why we often refer them as shadowy planets.