A daf that makes you reference another daf today! First, we see that God (yes God) has to brings. Sin offering for diminishing the size of the moon:
The Gemara objects: But this phrase is necessary in order to expound it in accordance with the statement of Reish Lakish, as Reish Lakish says: What is different about the goat brought as a sin-offering of the New Moon that it is stated with regard to it: “To the Lord,” a term not written with regard to other sin-offerings? The Holy One, Blessed be He, says, as it were: This goat shall be an atonement for the fact that I diminished the size of the moon.
Now the backstory come from Chullin 60:
Rabbi Shimon ben Pazi notes [a seeming contradiction in the text]: It is written, “And God made the two great lights” (Bereishit1:16), but it is also written [in the same verse] “The greater light to rule the day, and the lesser light to rule the night’” [implying that one was greater than the other].
(The explanation that follows presumes that originally, the sun and the moon were equally bright.)
The moon said before the Holy One, blessed be He: “Master of the Universe, is it possible for two kings to share the same crown?”
God therefore said to [the moon], “Go and diminish yourself.”
She said before Him: “Master of the Universe, just because I made a correct observation before You, I should diminish myself?”
God said to her: “Go and rule during both the day and the night.”
She said to Him: “Of what use is a candle at midday?”
God said to her: “Go; let the Jewish Peoplecount the days and years by you.”
She said to Him: “But they will count by the sun as well, for it is impossible that they will not count seasons that way, as it is written: ‘And let them be for signs, and for seasons, and for days and years’ (Bereishit 1:14).”
God said to her: “Go; let righteous men be named after you [as the light that is ‘katan’ – smaller/lesser]: there will be Yaakov Ha-katan, i.e., Yaakov [our forefather; see Amos7:2]; Shmuel Ha-katan [the Tanna, Shmuel); and David Ha-katan, [King David; see I Shmuel 17:14).”
God saw that the moon was not appeased. The Holy One, blessed be He, said: “Bring atonement for Me, since I diminished the moon.”
And this is as R. Shimon ben Lakish says: “What is distinct about the goat offering of Rosh Chodesh, concerning which we are told, ‘For the Lord’ (Bamidbar 28:15)? The Holy One, blessed be He, said: ‘This goat shall be an atonement for Me for having diminished the moon.’”