How do we determine the hour of dawn, when night ends and day begins?

I want to share a quote from a Hasidic Rabbi who asked his students “how do we determine the hour of dawn, when night ends and day begins?” One replied “When you can distinguish a sheep from a dog.” No said the Rabbi. “When you can distinguish a fig tree from a grapevine.” No, said the Rabbi. “Then tell us”. “It is when you can look into the face of human beings and have enough light to recognize them as your sisters and brothers.

Until then, it is night and darkness is still with us,” said the Rabbi.