The first of Tishrei is the demarcation for the beginning of the Sabbatical Year: Rosh HaShanah 2a, 8b
Whether the 1st or 10th of Tishrei marks the beginning of the Jubilee Year: Rosh HaShanah 2a, 7b, 8b
The first of Tishrei is the demarcation of the beginning of the year in counting for the prohibition against use of the First 3 Years of a tree's Produce: Rosh HaShanah 2a, 9b
The first of Tishrei is the demarcation between years in Tithing Vegetables: Rosh HaShanah 2a, 12a
The first of Tishrei is the demarcation between years in Tithing Grain: Rosh HaShanah 8a, 12a
Whether Abraham and Jacob were born in Tishrei or Nisan: Rosh HaShanah 10b, 11a
The verdict condemning the Generation of the Flood was set in the Month of Tishrei: Rosh HaShanah 12a
Cheshvan
Use of the term "Marcheshvan [lit. "Bitter Cheshvan", although there are other sources for the phrase]": Rosh HaShanah 7a, 11b
Whether the Flood began on the 17th of Cheshvan or of Iyyar: Rosh HaShanah 11b-12a
Either the 1st or 15th of Shevat is the demarcation date between years for separating Terumah on a tree's fruit from year to year: Rosh HaShanah 2a, 14a
Adar
We increase happiness in Adar: Taanit 29a-b
One who has a court appearance against someone who isn't Jewish [and hence doesn't share the special "luck" of Adar] should postpone it until Adar: Taanit 29b
On the first of Adar, the announcement to watch out for newly grown mixed-species was made: Megillah 13b, 29b
On the 15th of Adar, special money-changers were established to aid acquisition of the Half-Shekel for its donation to the Temple: Megillah 29b
On the 25th of Adar, special money-changers were established in the Temple itself to aid acquisition of the Half-Shekel for its donation to the Temple: Megillah 29b
Celebration of the 28th of Adar as a holiday: Rosh HaShanah 19a
Nisan
Nisan is also known as the month of "Ziv [Beauty]": Rosh HaShanah 11a
Nisan as the first of the months: Rosh HaShanah 2a, 7a
Nisan as the month symbolizing redemption: Megillah 6b
Whether the world was created in the month of Nisan, or the month of Tishrei: Rosh HaShanah 8a, 10b, 11a, 27a