(Mishnah): There are four Rosh Hashanos (New years) (two of which are listed in this Mishnah) -

The 1st of Nisan is the new year for kings and festivals;

The 1st of Elul is the new year for Maaser (tithing) of animals;

R. Elazar and R. Shimon disagree: It is on the 1st of Tishrei.

(Gemara): The Pasuk states (Shemos 12, 2), "This month will be to you the head of the months'' - to you it is the head but it is not the head of years, Shemitas, Yovels, saplings and vegetables.

Question: Perhaps you could say that it is head 'to you' but it is not the head of kings and festivals?

Answer (R. Yaakov bar Acha/ R. Yasa quoting R. Yochanan): The Pasuk states (Divrei Hayamim 2, 3, 2), "He (Shlomo) began to build in the 2nd month 'on the 2nd' in the 4th year of his reign''. The Pasuk compares the 4th year of his reign to the 2nd month - just as the 2nd month is only counted from the month of Nisan, so the 2nd month in the 4th year of his reign is counted from Nisan.

Question: Perhaps 'on the 2nd' refers to the 2nd day of the month?

Answer: Whenever the Torah speaks about the day of the month, it uses the phrase 'of the month'.

Question: Perhaps 'on the 2nd' refers to the day of the week?

Answer: The Torah does not recount details of the day of the week.

Question: But the Pasuk states (Bereishis 1, 8), "and it was the evening and it was the morning, the 2nd day''...?

Answer: One cannot learn from the creation of the world.

Question: Which '2nd' refers to the 2nd month and which '2nd' refers to the 2nd year?

Answer: R. Chananya and R. Mana disagreed - one said that "He began to build in the 2nd''- refers to the 2nd month and "in the 2nd'' refers to the 2nd year. The other one said that even if one says the opposite, it is fine.

R. Shimon bar Karsana quoting R. Acha: The Pasuk that states (Shemos 12, 2), "This month will be to you'' - is a phrase of exclusion; the later phrase "it is the first to you'' - is also a phrase of exclusion. It is an exclusion followed by an exclusion (which is an instruction) to include kings and festivals (that they also use the 1st of Nisan).

Question: Perhaps it should also include years, Shemitas, Yovels, saplings and vegetables?

Answer: It is like the statement of R. Yaakov bar Acha/ R. Yasa quoting R. Yochanan - "He began to build in the 2nd month 'on the 2nd' in the 4th year of his reign''. We compare the 4th year of his reign to the 2nd month - just as the 2nd month is counted from Nisan, so the 4th year of his reign is counted from Nisan.

R. Yona/ R. Yitschak bar Nachman quoting R. Chiya bar Yosef: "He began to build in the 2nd month'' - this refers to the 2nd of the months. "On the 2nd'' - this refers to the 2nd year. When the Pasuk says, "in the 4th year of his reign'', the 4th year is compared to the 2nd month - just as the 2nd month one only counts from Nisan; so the 4th year is only counted from Nisan.

Shmuel disagrees (Beraisa): The Pasuk states (Shemos 19, 1), "In the 3rd month of the exodus of Bnei Yisrael from the land of Egypt'' - from here we learn that one counts months from the exodus from Egypt (that took place in Nisan).

This is only a source for months; what is the source for years? The Pasuk states (Bamidbar 9, 1), "Hash-m spoke to Moshe in the wilderness of Sinai in the 2nd year''.

This only teaches a temporary law; what is the source that this applies in all generations? (Melachim 1, 6, 1), "It was in the 480th year from the exodus of Bnei Yisrael from the land of Egypt etc.''

After the construction of the Temple, they began counting from the time of its construction, as the Pasuk states (Melachim 1, 9, 10), "It was at the end of the 20 years in which Shlomo built the two buildings etc.''

When they did not merit counting from its construction (because the Temple was destroyed), they began to count from its destruction, as the Pasuk states (Yechezkel 40, 1), "In the 25th year of our exile, at the beginning of the year, on the 10th of the month etc.''

When they did not merit to count according to the Jewish kings, they began to count according to the gentile kings, as the Pasuk says (Chagai 1, 1), "In the 2nd year of Daryavesh('s reign)''; [as the Pasuk says] (Daniel 10, 1), "In the 3rd year of Koresh king of Persia''.

And the Pasuk says (Divrei Hayamim 2, 3, 2), "He began to build in the 2nd month 'on the 2nd' in the 4th year of his reign''. The 4th year of his reign is compared to the 2nd month - just as the 2nd month one only counts from Nisan; so the 4th year is only counted from Nisan.