What is the ruling on intentionally eating during the daylight hours of the past sixth and seventh days of Ramadan, after the cessation of menstrual bleeding on the fifth day, given that no blood appeared on these two days, and I purified myself on the night of the seventh day, and fasted the day that followed? And does this constitute an intentional breaking of the fast that necessitates expiation?

The signs of purity are: dryness of the area, or the white discharge. Whoever does not see either of these signs is considered to have the ruling of a menstruating woman. If you broke your fast due to not discerning purity, there is no sin upon you. However, if you saw a sign of purity then broke your fast while being aware of the religious ruling, then you are sinful, and repentance and making up the fast are incumbent upon you in both cases.