Yes, you can certainly have a housewarming function the day after Amavasya, which is the lunar phase of a new moon. The timing of a housewarming function is a matter of personal preference and cultural traditions. While some people may prefer to perform such events during auspicious days or specific lunar phases, others may choose dates that are convenient for them.
In many cultures, Amavasya is considered a period of low energy or inauspiciousness. Therefore, some individuals may avoid scheduling important events like housewarming ceremonies during this time. However, this belief can vary based on personal or regional customs and may not be universally followed.
Ultimately, the decision to hold a housewarming function the day after Amavasya is up to you and your personal beliefs or traditions. If you are unsure or want to align with specific customs, you may consider consulting with an astrologer or seeking advice from individuals familiar with the cultural and astrological practices relevant to your situation.