(Mishnah): The 1st of Tishrei is the New Year for [counting] years, the Shemita and Yovel cycles, for planting and for vegetables.

Beis Shamai: The 1st of Shevat is the New Year for trees.

Beis Hillel: On the 15th [of Shevat].

(Gemara): [The new year for counting years] - what is the source for this? One Pasuk states (Shemos 23, 16), "and the festival of gathering, at the end of the year''. Another Pasuk states (Shemos 34, 22), "and the festival of gathering, at the changing of the year.''

Which month has a festival, a change, a gathering (of crops) and the year ends? It is the month of Tishrei.

If you suggest that it is Teves, it has a change, but it does not have a festival or a gathering. If you suggest that it is Nisan, it has a change but it does not have a gathering. If you suggest that it is Tamuz, it has a change and a gathering but it does not have a festival. Therefore, we must be referring to the month of Tishrei.

Question (Chevraya to R. Yona): Why can it not be Tamuz (and let Rosh Hashanah and Sukos occur in Tamuz)?

Answer (R. Yona): The Pasuk states "in the 7th month'' and you wish to suggest this?!

Question (Chevraya): Let the 7th month be called Tamuz?

Answer (R. Yona): Are you starting to question me about the names of the months? R. Chanina said that the names of the months were brought with those that returned from Bavel.

R. Yona explains: The 7th month was originally called the month of 'Aysanim' (the mighty ones) - the month in which the fathers (Avraham and Yaakov) were born and passed away, and the month in which the mothers (Sarah and Rachel) were remembered and became pregnant.

Firstly, concerning the month of Kislev, the Pasuk states (Melachim 1, 6, 38), "...in the month of Bul [which is the 8th month]'' - the month in which the leaves shrivel and the land turns into clumps (because it is muddy). It is the month in which food is mixed for the animals inside the house (as there is no more food growing in the field).

Firstly, concerning the month of Iyar, the Pasuk states (Melachim 1, 6, 37), "...in the month of Ziv'' - the month in which the brightness of the world - the vegetation, is visible and the trees are visibly living.

After they returned from Bavel, the Pasuk states (Nechemya 2, 1), "It was in the month of Nisan in the 20th year.'' And another Pasuk states (Nechemya 1, 1), "It was in the month of Kislev in the 20th year.'' A third Pasuk states (Esther 2, 16), "In the 10th month, the month of Teves''. (In all of these Pesukim, the modern names were used.)