Garudapurana 1.59.26

1.59.26

amāvāsyā pūrṇimā ca tadvādaśī ca caturdaśī /
aśuklā pratipacchreṣṭhā dvitīyā candra sūnunā //

new moon, full moon, and likewise the twelfth and fourteenth. / The dark first lunar day is auspicious; the second is best with the son of the Moon [Mercury];