Why did astrologers try to stop the declaration of August 15 as Independence Day in 1947?

Some Indian astrologers had tried to stop the declaration of August 15 as Independence Day in 1947. The last Viceroy of India, Lord Mountbatten, had claimed that astrologers had declared August 13 and 15 as inauspicious days and August 14 ad auspicious. Notably, an astrologer had even written to Mountbatten, pleading him not to grant India independence on August 15.