In Jain dharma there is no canonical rule that says sex on a particular tithi (lunar day) is right or wrong. The conduct expected of a lay Jain is guided by general ethical principles: non-violence (ahimsa), truthfulness, self-control, respect for consent, and fidelity within the bounds of marriage.

Key points:

• For lay followers: sex is considered appropriate within a lawful, loving, and consensual marriage, and should be practiced with restraint and without causing harm or exploitation.
• For monks and nuns: celibacy is mandatory; sexual activity is not allowed at all.
• There isn’t a specific Jain rule that links sexual conduct to the phase of the moon or a single tithi. The emphasis is on ethical self-discipline, purity of intention, and the well-being of all involved.

If you want, I can explain how Jain texts describe sexuality and ethical conduct in more detail, or point to traditional dharma principles that guide daily behavior.