הלכות נדרים

When a person takes a vow or an oath, saying: "I will not taste [food] today," he is forbidden only until nightfall. [If he said]: "I will not taste food for one day," he is forbidden [to eat] for a twenty-four hour period after taking his vow. Accordingly, even though he is permitted [to eat] after nightfall, one who takes a vow "not to taste [food] today" should not eat after nightfall until he asks a sage [to retract his vow]. [This is] a decree lest he take an oath another time not to eat for an entire day and eat after nightfall. For people at large do not know the difference between these two situations.

When one takes a vow, saying: "I will not taste [food] a day," there is an unresolved question. 60a discusses this issue without reaching a conclusion. [Hence] he is forbidden to [eat] for an entire day, as if he had said "for one day." If he eats after nightfall, he does not receive lashes.
When one takes a vow, saying: "I will not taste [food] during this week,", which literally means "Sabbath." Nevertheless, his intent (and that of his source, Nedarim 60a) is obviously a week and not the holy day itself.
When stating this law, the Shulchan Aruch (Yoreh De'ah 220:3) uses the term shavua for "week," rather than Shabbat. The Turei Zahav 220:2 states that the Shulchan Aruch's ruling applies when the person taking the vow speaks in lashon hakodesh, "the holy tongue." If, however, he would speak in Yiddish and say di voch, "this week," the Sabbath is not included, because the term voch implies ordinary, weekdays that are different in nature than the holy Sabbath. he is forbidden to eat during the remainder of the week and on the Sabbath, but he is permitted on Sunday. [When he says:] "I will not taste [a type of food] 1:7. for one week," he is forbidden to eat [that type of food] for seven full days. If he says "[I will not eat a type of food] a week," there is an unresolved question. [Hence] he is forbidden to [eat that type of food] for seven full days. If he eats after the Sabbath, he does not receive lashes, as we explained.

[When one takes a vow, saying:] "I will not drink [wine] during this month," he is forbidden in the remaining days of the month. He is, however, permitted on the day of the following Rosh Chodesh even if the month is lacking., chs. 1-3, which discusses the principles determining when a month is given only 29 days and when it is given 30].
The commentaries question why the Rambam (based on Nedarim 60b) speaks of the month being lacking. Seemingly, it is quite obvious that if there are only 29 days in a month, one would be permitted on Rosh Chodesh in the next month. The new month has already begun. A point that has to be made is that even if there are 30 days in a month, one is permitted to partake of wine on the thirtieth day. Since it is Rosh Chodesh of the coming month, the vow has concluded even though the date is the thirtieth of the previous month.
The Radbaz explains that this in fact is the Rambam's intent, even though his wording is somewhat difficult to explain in that manner. This interpretation is reflected in the wording of the Shulchan Aruch (Yoreh De'ah 220:4). The Or Sameach offers a different interpretation, stating that when a month has only 29 days, sometimes the conjunction of the sun and the moon does not take place until the first day of the new month. Even so, since it is already Rosh Chodesh, the vow is concluded. [If he took a vow, saying]: "I will not drink [wine] for an entire month," he is forbidden for 30 full days. [If he said]: I will not drink [wine] for a month," he is forbidden for 30 full days because of the unresolved question.

[When one takes a vow, saying:] "I will not eat meat this year," even if there is only one day left in the year, he is forbidden only that day and is permitted to eat [meat] on Rosh HaShanah. For the beginning of the year with regard to vows is Rosh Chodesh Tishrei.
[If he says:] "I will not eat [meat] for one year," he is forbidden for a complete year from day to day. If it is a leap year,, ch. 4. he is forbidden in that year and in the extra month. [If he says]: "I will not eat [meat] for a year," he is forbidden for a complete year from day to day, because of the unresolved question as explained.

[When one takes a vow, saying:] "I will not drink wine this seven-year cycle," he is forbidden in the remaining years of the seven year cycle and in the Sabbatical year. He is not permitted until Rosh HaShanah of the year after the Sabbatical year.
[If he says:] "I will not drink wine for a seven-year cycle," he is forbidden for seven full years from day to day. [If he says: "I will not drink wine] this Jubilee cycle, he is forbidden in the remaining years of the Jubilee cycle and in the fiftieth year itself.

[The following rules apply when one says:] "I will not drink wine until Rosh Chodesh Adar: If it was a leap year, but he did not know that it was a leap year when he took the vow, he is forbidden only until Rosh Chodesh Adar I. If he took the vow until the end of Adar, he is forbidden until the end of Adar II. If he did know that it was a leap year, he is forbidden until Rosh Chodesh Adar II. 63a) which of the two months Adar is considered as Adar and which is the additional month. There are other authorities who follow a different version of the passage in Nedarim and maintain that he is always forbidden only until the beginning of Adar I.
The Shulchan Aruch (Yoreh De'ah 220:8) mentions the Rambam's view as a minority opinion. The commentaries note that in other places in the Shulchan Aruch (Choshen Mishpat 43:28, Rama, Even HaEzer 126:7), the Rambam's view is not cited at all.

When a person forbids himself from benefiting from a substance until Pesach, whether he said "until before Pesach" or "until Pesach," he is only forbidden until the holiday commences. If he says: "while it is Pesach," he is forbidden until Pesach concludes. If he said: "until the wheat harvest" or "until the grape harvest," or "while it is the grape harvest" or "while it is the wheat harvest," he is forbidden only until that time arrives.

This is the general principle: Whenever there is a fixed time for a subject mentioned in a vow, he is forbidden only until that time comes. If he words [his vow] "as long as it is," he is forbidden until that time concludes. Whenever a subject does not have a fixed time - like the time of the wheat harvest or the grape harvest - whether he said "until" or "while it is," he is forbidden only until that time arrives.

When a person forbids himself [from benefiting from] a substance until the kayitz, 8:3), the Rambam defines this as referring to the period from the end of Tammuz until the end of Elul when figs ripen and are ready for harvesting. he is forbidden until the people in his place begin bringing in baskets of figs. [If he vowed] until the katzir, [he is forbidden] until people will harvest wheat, but not barley.).
If he explicitly said: "...until the kayitz passes," he is forbidden until the majority of the people fold up the mats they have set aside to dry figs and grapes to produce dried figs and raisins. Everything depends on the local practice in the place where the person took his vow.

What is implied? If he took a vow in a valley and forbid himself [from benefiting] from a substance until the kayitz and then moved to a mountainous region, he should not pay attention to the time whether or not the fig harvest has begun in the place where he is at present. Instead, [he is concerned] with when it begins in the place where he took the vow and that is what he follows. (Yoreh De'ah 220:13). Similar laws apply in all analogous situations. in a place where the primary crop is barley, he is forbidden until the beginning of the barley harvest (ibid.:14).

When a person forbids himself [from benefiting] from a substance until "the rains," he is forbidden until the rainy season which in Eretz Yisrael [begins] on Rosh Chodesh Kislev. When the time of the rainy season arrives, he is released [from his vow] whether it rains or not. If, however, it rained from the seventeenth of MarCheshvan, he is released. 7:5), rain at that time is not considered a chance occurrence and the vow is released. See Hilchot Ta'aniot 3:1-2 and Hilchot Matanot Aniyim 1:11 which also discuss these times for rain.
If he said: "...Until it rains," he is forbidden until it rains, provided it rains from the second phase of the preliminary rainy season.), the Rambam interprets the term reviah as referring to the time when rain descends, explaining that it is similar to the term used for impregnating a woman, because in both cases, the potential for life is granted. In Eretz Yisrael and in the places close to it, this is from the twenty-third of MarCheshvan onward. If he explicitly said: "...until the rains cease," he is forbidden until the conclusion of Pesach in Eretz Yisrael and in the places like it.

When a person has his wife bound by a vow in MarCheshvan, telling her: "You may not benefit from me from now until Pesach if you go to your father's house from now until Sukkot," she is forbidden to benefit from him immediately. [This is] a decree for perhaps she will go. If she went before Pesach and derived benefit from him before Pesach, he is liable for lashes. 57b) differ with the Rambam and maintain that the woman is liable for lashes.
If Pesach passed, even though the stipulation has expired, it is forbidden for him to treat the vow casually and allow her to go [to her father's home] and derive benefit from him. explains that he should continue to withhold benefit from her, for that is the only way that he can insure that she will keep the vow. The Ra'avad and others differ with the Rambam concerning the need for this safeguard and their view is accepted by the Shulchan Aruch (Yoreh De'ah 220:22). Instead, he should treat her as if it is forbidden until Sukkot as he vowed. [This applies] even though he made the vow dependent on a time that has already passed. Similar laws apply in all analogous situations. If she went [to her father's home] after Pesach, she is not forbidden to benefit from him.

If he told her: "You may not benefit from me from now until Sukkot if you go to your father's house from now until Pesach," she is forbidden to benefit from him immediately. If she went [to her father's home] before Pesach and he gave her benefit, he is subject to lashes. She remains forbidden to him until Sukkot. After Pesach arrives, she is permitted to go to her father's house.