I thought according to Hinduism, it is proper for woman to conceive at night. If she conceives at daytime, the children are weak and short-lived. I read it on a website that has explicit paintings, hence I didn't provide the link.
However, I am watching Shiv Mahapuran and this episode mentions how demons and gods belong to same father, Sage Kashyap. However, the mother of the demons, Diti desires to conceive at night so that her children can become strong like demons.
Here is the YouTUBE link, starting at that scene (26 minutes and 10 seconds)
Please clarify, what is the Hindu belief on best time a woman should conceive for healthy, honest, children.