Today’s Shrāvana Poornima/Full Moon which lasted till 7.05 AM on 12th August Indian Standard Time marks the beginning of 6th Vedic month called as Bhadrapada. Shrāvana Poornima is also the day when Raksha-Bandhan popularly known as Rakhi is celebrated. This festival celebrates the sanctity and beauty of brother-sister relationship. Traditionally, sisters tie rakhi across the wrist of their brothers and they pray for each other’s good and prosperous life.
What is Bhadra Kaal?
Vedic astrology suggests that any auspicious activity shouldn’t be done during the Bhadra Kaal. My little research tells me that Ma Bhadra is the daughter of Surya Dev and sister of Shani Dev/Saturn. She has been given a special place in Hindu Panchang. Her state/loka changes when Moon changes rashi.
This looks like a good resource for someone wanting to know more about Bhadra Kaal: https://www.astroswamig.com/articles/bhadra-in-astrology