As the name suggests, this day is observed when the asterism of Pooram is in the ascendant in the Tamil month of Aadi. The asterism of Pooram is contained in the zodiacal sign of Leo (simmaraasi); this means that the moon is in simmaraasi on this day; the sun, on the other hand, is in the zodiacal sign of Cancer (kadaharaasi) on this day. The planetary lord for simmaraasi is the sun and for kadaharaaasi, the moon. The day of Aadippooram is significant on this basis, where the sun is in the ruling house of moon and vice versa.
Aadipporam falls in line with the fact that the month of Aadi is auspicious for Devi.