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

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Vesatot with 28-day cycle

27 November, 2006


I've been reading your articles on vestos and am more confused than ever. Can you settle confusion about the veset kavua? My periods are pretty regular, coming at intervals of 27 or 28 days. I realize now that an actual veset kavua is an exact interval even down to the daytime or nightime. Mine were never like that, but the point is that I never go past 28 days, ever. So I've never had to observe the same day of the Hebrew month (which would be approximately a 30 day interval) or the onah beinonit. As far as I know, I only have one veset to observe, correct? Thanks!


If you always menstruate before day 30 of your cycle, you are correct that you will observe only the interval. This is not because you have a veset kavua, but because you get your period before reaching your other veset days. If you ever do get your period later, you will keep yom hachodesh and onah beinonit like any woman who does not have a veset kavua.

Everything you wrote shows a correct understanding of the concept of veset kavua. A woman with a veset kavua gets her period either at regular intervals or on regular dates on the Hebrew calendar. This veset needs to be precise not just to the date, but to the daytime or night time.

If there is variation within the range of a few days, or even day and night of the same day, is not a veset kavua. However, if you consistently become niddah on day twenty-seven or day twenty-eight, then you should observe both days as an interval day each month unless or until you etablish one of them as a veset kavua.

Please feel free to follow up if this is unclear!

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