Nishmat's Women’s Health and HalachaIn memory of Chaya Mirel bat R' Avraham

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Veset Hayamim (Dates of anticipated menses)

A woman anticipates her menses on certain days called vestot (singular veset), based on her previous menstrual cycle pattern. Each veset day is observed as an onat perishah (period of separation). Marital relations are forbidden and the woman performs a bedikah (internal examination) to check whether she has begun to menstruate.

veset based on calendar dates is called veset hayamim (as opposed to a veset haguf, which is based on physical sensations accompanying menstruation).

Most women observe three types of vestot hayamim, which are calculated from the onset of their previous menses:

1) The same date of the Hebrew month, or yom hachodesh. If, for example, a woman began menstruating on the 15th of Nisan, then she anticipates her next menses on the 15th of Iyar.

2) The interval day, or haflagah. A woman anticipates that she will menstruate after the same interval as that which separated her previous two periods. If, for example, her last menses began 27 days after the beginning of the previous menses, then she anticipates her next menses 27days after the beginning of the last menses.

3) The thirtieth day from the onset of her previous menses, called the onah beinonit, the average interval.

Somewhat different rules apply to a woman with a veset kavua, a completely regular period as defined by halacha.

Each veset lasts for one onah, either daytime or night-time, corresponding to the beginning of the immediately preceding menses. For example, a woman who began menstruating during the day, and whose next period began after a 27-day interval at night, will anticipate her menses after a further 27-day interval at night.

According to some customs, additional periods of separation are required (some such customs are cited in onot perishahonah beinonit). A custom adopted by a community as a whole is binding upon the entire community. Where there is no local custom, a couple inclined to observe these stringencies should consider the matter carefully and discuss it with a rabbi, as it would be halachically difficult for them to revert to the more lenient custom should they later wish to do so.

Jewish Lunar Months

The Jewish lunar months and their approximate solar equivalents are as follows:

Nisan (March/April)

Iyar (April/May)

Sivan (May/June)

Tammuz (June/July)

Av (July/August)

Elul (August/September)

Tishrei (September/October)

Cheshvan (October/November, also called Marcheshvan,)

Kislev (November/December)

Tevet (December/January)

Shevat (January/February)

Adar (February/March, in a leap year there are two Adars, Adar I and Adar II)

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All health and health-related information contained within Nishmat's Women's Health & Halacha Web site is intended to be general in nature and should not be used as a substitute for consulting with your health care professional. The advice is intended to offer a basis for individuals to discuss their medical condition with their health care provider but not individual advice. Although every effort is made to ensure that the material within Nishmat's Women's Health & Halacha Web site is accurate and timely, it is provided for the convenience of the Web site user but should not be considered official. Advice for actual medical practice should be obtained from a licensed health care professional.

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