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

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Day/night for interval

22 January, 2005


My period started today, Shabbos afternoon, 12 Shevat. The Interval Onah is 28 days from now, since my last cycle was 28 days. The bleeding last month started during the night Onah (12-hour period). This time, however, it started during the day Onah.

When is the next Interval Onah, given that the bleeding began during the evening last time and during the day this time? Which calendar day next month (and which part of that day) do I keep?


As long as you do not have a veset kavua (a pattern, which repeated itself at least three times, of getting your period either at regular intervals or on the same day of the month), you always keep the days of separation according to the previous month's dates. In this case, if you got our period during the day, your 28-day interval (haflagah) comes out on Friday, 9 Adar, during the day. You will also separate on two other days: Shabbat, 12 Adar, during the day (the day of the month), and Sunday, 11 Adar, which is your onah beinonit (thirty day interval, which all women have to keep.)

The onah of separation is always based on the previous month, so if you got your period during the day you keep the day onah (sunrise to sunset), and if you got your period at night your onah is the following month is at night (sunset to sunrise).   

Please note that Chabad has a different custom — and write back if this is relevant to you.

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