The Sages offer various suggestions regarding the effect that the time of a person’s birth, both the day of the week and the hour, has on his character.

It was written in Rabbi Yehoshua ben Levi’s ledger: One who was born on the first day of the week will be a person who will not have one in him. What is the meaning of: Who will not have one in him? If you say that there is not one good quality in him, that is difficult: But didn’t Rav Ashi say: I was born on the first day of the week [and he certainly had good qualities]. Rather, it means that there is not one bad quality in him. But didn’t Rav Ashi say: Dimi bar Kakuzta and I were born on the first day of the week; I am a king [head of a yeshiva], and he became head of a gang of thieves. Rather, one born on the first day of the week is either completely good or completely bad. What is the reason? It is because light and darkness were created on the first day of Creation.

One who was born on the second day of the week will be an irritable person. What is the reason? It is because on that second day of Creation, the upper and lower waters were divided.

One who was born on the third day of the week will be a rich man and an adulterer. What is the reason? It is because on that third day of Creation, vegetation was created.

One who was born on the fourth day of the week will be a wise and enlightened person. What is the reason? It is because the lights were suspended in the heavens on that fourth day.

One who was born on the fifth day of the week will be a person who performs acts of kindness. What is the reason? It is because on that day fish and birds were created.

One who was born on the day before Shabbat will be a seeker. Rav Nahman bar Yitzhak said: This means he will be a seeker of mitzvot.

One who was born on Shabbat will die on Shabbat, because the great day of Shabbat was already desecrated once on his behalf. Rava bar Rav Sheila said: He will be called a person of great sanctity.

Rabbi Hanina said to his students: Go tell Rabbi Yehoshua ben Levi: It is not the astrology of the day of the week that determines a person’s nature; rather, it is the astrology of the star of the hour that determines his nature.

One who was born under the influence of the sun will be a radiant person. He will eat from his own resources and drink from his own resources, and his secrets will be exposed. If he steals, he will not succeed.

One who was born under the influence of Venus will be a rich and adulterous person. What is the reason? It is because fire was created in it.

One who was born under the influence of Mercury will be an enlightened man, because Mercury is the sun’s scribe.

One who was born under the influence of the moon will be a person who suffers pains, who builds and dismantles, and dismantles and builds. He eats not from his own resources and drinks not from his own resources, and his secrets are hidden. If he steals, he will succeed.

One who was born under the influence of Saturn [Shabbetai] will be a man whose plans are constantly nullified. And some say that everything that others think [or plot against him] will be nullified.

One who was born under the influence of Jupiter [Tzedek] will be a just person [tzadkan]. Rav Nahman bar Yitzhak said: He will be just in the performance of mitzvot.

One who was born under the influence of Mars will be one who spills blood. Rav Ashi said: He will be either a bloodletter, a thief, a ritual slaughterer, a butcher, or a circumciser. Rabba said: I was born under the influence of Mars and I do not perform any of those activities. Abaye said: My master also punishes and kills [in his capacity as a judge]. (Shabbat 156a)