In the situation you describe, even though the staining you found was definitely from the earlier
onah, it did not make you
niddah because it was on
colored sheets. Even if the staining were larger than a
gris and found on a white garment (which would make you
niddah), the
five day minimum would be counted from the later
onah because you did not consider yourself
niddah during the earlier
onah.
Onot perishah are not calculated from staining, only from the onset of actual menstrual bleeding. Therefore, earlier staining – whenever it is discovered, and whether or not it makes you
niddah – will not affect your
veset calculations.
In a situation where a woman discovers bleeding and is unsure whether it began during that
onah or the previous
onah, she counts day 1 of her period (both for
vesatot and for the five day minimum) from the
onah in which she discovered the bleeding. This is true for
veset calculations because she definitely was bleeding during the later
onah, but there is doubt about whether she experienced bleeding during the previous
onah. It is true for the five day minimum because that is counted from the point at which she considers herself
niddah.
Please feel free to get back to us with any further questions.
