Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.3.11

2.6.3.11

taddhaike | rātrīrāpipayiṣanti sa yadi rātrīrāpipayiṣedyadadaḥ purastātphālgunyai paurṇamāsyā uddṛṣṭaṃ tacunāsīryeṇa yajeta

Here now some wish to take possession of the nights; and should he wish to take possession of the nights, let him offer the Sunâsîrya (on the day) when, previously to the full-moon of Phâlguna, (the new moon) becomes visible in yonder sky.