A person who sells a house within a walled city has the right to buy it back for 12 months.
R. Nehorai says that Avshalom cut his hair once every 12 months.
R. Yosi says that Avshalom cut his hair every Erev Shabbos.
R. Yishmael says that a Gezeirah Shavah can be learned out even though the words are not exactly the same. (1)
A Kohen who does the Avodah must cut his hair every thirty days.
The rebellion of Avshalom occurred forty years after Klal Yisrael requested a King. (2)
Rav Masna says that a Stam Nezirus is for thirty days.
Bar Pada says a Stam Nezirus is for twenty-nine days.
A Nazir is forbidden to drink wine even for a Mitzvah.
One Nezirus takes effect on top of another Nezirus. (3)
A Stam Nazir may shave on the thirty-first day but if he shaves on the thirtieth day he is Yotzei. (4)
If a person says that he will be a Nazir for a complete thirty days if he shaves on the thirtieth day he is not Yotzei.
If someone takes upon himself two Neziruyos he shall shave for the first Nezirus on the thirty-first day and for the second Nezirus on the sixty-first.
A BIT MORE
1. However if it is possible to learn it out from the same word we may not learn it from a different word.
2. The year that Klal Yisrael asked for a King was the tenth year of the reign of Shmuel as a Shofet of Klal Yisrael.
3. If someone says he shall be a Nazir today and then he says again he shall be a Nazir today he must count two separate Neziruyos.
4. Even according to R. Masna b'Di'eved he may shave on the thirtieth day because he holds that part of a day is regarded as a complete day. According to Bar Pada who holds that a Stam Nezirus is for 29 days, although l'Chatchilah the Rabanan decreed that a Nazir may not shave until the thirty-first day because of a Gezeirah of a case in which he says that he will be a Nazir for a complete thirty days, b'Di'eved if he shaves on the thirtieth day it is valid.
Rav Masna says that we learn out that Stam Nezirus is for thirty days from the numerical value of Yiheyeh which is thirty. The Rambam in his commentary on the Mishnah says that we learn from a Halachah l'Moshe mi'Sinai that a Stam Nezirus is for thirty days and the Limud from Yiheyeh is an Asmachta. The Rosh explains that a Limud from a numerical value is not one of the Midos with which we are Doresh the Torah and therefore the Din of Stam Nezirus may not be learned out solely from the numerical value.
Stam Nezirus is for thirty days. What is the case? If someone says he shall be a Nazir he is a Nazir for thirty days. Even if he says that he shall be a Nazir with a very big Nezirus he is only a Nazir for thirty days because he did not specify an amount of time. If he specifies an amount of time which is less than thirty days, such as if he says he shall be a Nazir for one day or ten days or twenty days, he is a Nazir for thirty days because Nezirus may not be for less than thirty days. This is a Halachah that is learned from Kabalah. (Rambam Hilchos Nezirus 3:1,2)