Answered by Shaykh Faraz Rabbani
I woke up yesterday and the time for sehri had past and there was about 45 minutes left for fajr, would my fast be accepted because I made my intention after the time for sehri had past?
As for the intention in fasting, you can make the intention to fast anytime until the Islamic mid-day, which is half-way between the time fajr comes in and when maghrib comes in. [Around an hour before Zuhr.] An intention may be made any time from Maghrib of the night before, and remains valid as long as you did not resolve NOT to fast.
Note, however, that an “intention” [go back and read the posting on Intention] is “a firm resolve to perform an act of worship,” and, as such, it is rarely conceivable that a Muslim NOT have an intention in Ramadan, the scholars tell us. And even the intention to get up for Suhur is considered sufficient for validity.
And Allah knows best.