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

  • Hebrew
  • English
  • Espnaol
  • Francais
  • donate

Calculations with missing veset date

11 September, 2014


I had thought that I wrote down the date⁄time when my last period began, but I just went to look and cannot find it –– so do not know how to determine times for separation in my calendar. I have been calculating for irregular cycle –– yom hachodesh, haflagah, onah beinonit. I do have the dates for my previous three periods –– all in the night onah. I can remember the date of my hefsek and mikvah night but do not recall when my period began. Thanks:


There are different halachic approaches to this situation. We recommend that you try to reconstruct the day your period began, based on the usual interval from the start of your period to your hefsek taharah (e.g. five to seven days). Was there some event during those that you and your husband attended when you were or were not niddah?  Does your husband have any recollection?  Are you reasonably sure it was at night, as your other recent onot have been? 

If one night of that range seems more likely, you should calculate your onot based on it.  Otherwise, you should count backwards five days from your hefsek taharah (the day of the hefsek is day five and you're counting back to day one) and count that as your veset, since by then you were certainly in niddah.

Please write back with any further questions.

This internet service does not preclude, override or replace the psak of any rabbinical authority. It is the responsibility of the questioner to inform us of any previous consultation or ruling. As even slight variation in circumstances may have Halachic consequences, views expressed concerning one case may not be applied to other, seemingly similar cases. 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.

For further questions or comments: 

The Nishmat Women's Health and Halacha Site is a public service of Nishmat, The Jeanie Schottenstein Center for Advanced Torah Study for Women. This project and others like it are made possible by contributions from people like you. If you have benefited from the service, and wish to enable us to help others, click here to donate.

Users of Internet filtering services: This site discusses sensitive subjects that some services filter without visual indication. A page that appears 100% complete might actually be missing critical Jewish-law or medical information. To ensure that you view the pages accurately, ask the filtering service to whitelist all pages under

Accessibility Toolbar