גמ׳ אמר רב חנן בר רבא קלנדא ח' ימים אחר תקופה סטרנורא ח' ימים לפני תקופה וסימנך (תהלים קלט, ה) אחור וקדם צרתני וגו'ת"ר לפי שראה אדם הראשון יום שמתמעט והולך אמר אוי לי שמא בשביל שסרחתי עולם חשוך בעדי וחוזר לתוהו ובוהו וזו היא מיתה שנקנסה עלי מן השמים עמד וישב ח' ימים בתענית [ובתפלה]כיון שראה תקופת טבת וראה יום שמאריך והולך אמר מנהגו של עולם הוא הלך ועשה שמונה ימים טובים לשנה האחרת עשאן לאלו ולאלו ימים טובים הוא קבעם לשם שמים והם קבעום לשם עבודת כוכבים
GEMARA:Rav Ḥanan bar Rava says: When are these festivals celebrated? Kalenda is celebrated during the eight days after the winter solstice, and Saturnalia is celebrated during the eight days before the winter solstice. And your mnemonic to remember which festival is that the one that occurs after the solstice is mentioned first in the mishna, and the festival that takes place before the solstice is mentioned after, as in the verse: “You have hemmed me in behind and before, and laid Your Hand upon me” (Psalms 139:5), where the word “before” appears after the term “behind.”With regard to the dates of these festivals, the Sages taught: When Adam the first man saw that the day was progressively diminishing, as the days become shorter from the autumnal equinox until the winter solstice, he did not yet know that this is a normal phenomenon, and therefore he said: Woe is me; perhaps because I sinned the world is becoming dark around me and will ultimately return to the primordial state of chaos and disorder. And this is the death that was sentenced upon me from Heaven, as it is written: “And to dust shall you return” (Genesis 3:19). He arose and spent eight days in fasting and in prayer.Once he saw that the season of Tevet, i.e., the winter solstice, had arrived, and saw that the day was progressively lengthening after the solstice, he said: Clearly, the days become shorter and then longer, and this is the order of the world. He went and observed a festival for eight days. Upon the next year, he observed both these eight days on which he had fasted on the previous year, and these eight days of his celebration, as days of festivities. He, Adam, established these festivals for the sake of Heaven, but they, the gentiles of later generations, established them for the sake of idol worship.
While Adam stood in the river, he noticed that the days were growing shorter, and he feared the world might be darkened on account of his sin, and go under soon. To avert the doom, be spent eight days in prayer and fasting. But after the winter solstice, when he saw that the days grew longer again, he spent eight days in rejoicing, and in the following year he celebrated both periods, the one before and the one after the solstice. This is why the heathen celebrate the calends and the saturnalia in honor of their gods, though Adam had consecrated those days to the honor of God. The first time Adam witnessed the sinking of the sun he was also seized with anxious fears. It happened at the conclusion of the Sabbath, and Adam said, "Woe is me! For my sake, because I sinned, the world is darkened, and it will again become void and without form. Thus will be executed the punishment of death which God has pronounced against me!" All the night he spent in tears, and Eve, too, wept as she sat opposite to him. When day began to dawn, he understood that what he had deplored was but the course of nature, and be brought an offering unto God, a unicorn whose horn was created before his hoofs, and he sacrificed it on the spot on which later the altar was to stand in Jerusalem.
Nor is this world inhabited by man the first of things earthly created by God. He made several worlds before ours, but He destroyed them all, because He was pleased with none until He created ours. But even this last world would have had no permanence, if God had executed His original plan of ruling it according to the principle of strict justice. It was only when He saw that justice by itself would undermine the world that He associated mercy with justice, and made them to rule jointly. Thus, from the beginning of all things prevailed Divine goodness, without which nothing could have continued to exist. If not for it, the myriads of evil spirits had soon put an end to the generations of men. But the goodness of God has ordained, that in every Nisan, at the time of the spring equinox, the seraphim shall approach the world of spirits, and intimidate them so that they fear to do harm to men. Again, if God in His goodness had not given protection to the weak, the tame animals would have been extirpated long ago by the wild animals. In Tammuz, at the time of the summer solstice, when the strength of behemot is at its height, he roars so loud that all the animals hear it, and for a whole year they are affrighted and timid, and their acts become less ferocious than their nature is. Again, in Tishri, at the time of the autumnal equinox, the great bird ziz flaps his wings and utters his cry, so that the birds of prey, the eagles and the vultures, blench, and they fear to swoop down upon the others and annihilate them in their greed. And, again, were it not for the goodness of God, the vast number of big fish had quickly put an end to the little ones. But at the time of the winter solstice, in the month of Tebet, the sea grows restless, for then leviathan spouts up water, and the big fish become uneasy. They restrain their appetite, and the little ones escape their rapacity.
Welcome to the month of Tevet! Tevet is often called “the month of contradictions” because while the word “Tevet” shares a root with “tov”, meaning goodness, this month is also known in the Sefer Yetzirah as the month of anger. As we, the people who wrestle, continue to dismantle “light supremacy” and lift up and fall in love with the darkness of this season, we also hold that anger is sacred and indeed, good too.
~Otzar haMidrashim, Hashem Bechachmah Yasad Aretz 6