תּלמוד אויף ויקרא 15:28

MISHNAH: For a sufferer from gonorrhea after two episodes one slaughters on the seventh {day}, if he had three episodes one slaughters for him on the eighth. Similarly for a woman watching day for day one slaughters on the second, if she had episodes on two consecutive days one slaughters on the third; but for the sufferer from flux one slaughters on the eighth⁹⁵A person who suffers a single episode of gonorrhea is impure for the day and can be purified by immersion in a miqweh. If he has two episodes in at most two consecutive days, he is impure for seven days; after seven days in remission he can be purified by immersion in a miqweh. After three episodes he still needs seven days in remission but then is still prohibited sancta unless on the eighth day he brings a couple of birds as sacrifice to the Temple. He can subscribe to a Pesaḥ if there is a reasonable chance that he will be permitted sancta after nightfall.
A menstruating woman is impure for seven days, Lev. 15:19. A woman having non-menstrual discharges for many days (Lev. 15:25), interpreted as three days, is in the same situation as a male sufferer from gonorrhea after three episodes (15:28–29). For isolated episodes on one or two days, she may immerse herself in a miqweh on the next day and become pure for sancta at nightfall..

and counting must be by day.

Abbai said : Like that of R. Zera who stated : The daughters of Israel are very strict with themselves ; for if they see even a drop of menstrual flow as small as a mustard seed, they wait seven clear days after it.