I vaguely remember reading somewhere that during Navratri the entire period is auspicious; shubh muhurta, Rahukalam, nakshatra, Chandrabalam, Tarabalam etc. do not matter for these nine days. Unfortunately I cannot recall the source.
Is there any support in scripture or modern astrological texts for the above-mentioned idea? If yes, does it refer to all four Navratris or only the Sharadiya one?