Before dawn, at the end of my menstrual period in the month of Ramadhaan, I expected the bleeding to end during the day - knowing that it was the last day of it – so I made the intention to fast. No blood appeared throughout the day and I performed Ghusl (i.e. ritual bath) half an hour before Maghrib.
Is my fasting of this day counted or should I make up for it?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If you came to know of your state of purity before dawn either by seeing a white discharge or by observing complete dryness, then you are considered pure and your fasting is valid if you had the intention to fast since [the previous] night. However, you made a mistake because you did not perform Ghusl and pray the obligatory prayers on time. You should make up for the prayers after performing Ghusl. If you did not see either of the two signs that mark the end of menstruation at any time during the night, then your fast is invalid. You should make up for it because one of the conditions of the validity of fasting is purity from menstruation and post-partum bleeding from the beginning of the day until its end. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Is it not true that none of you women should pray nor fast when menstruating?" [Al-Bukhari] 

Allaah Knows best.