Changing one's niyyat before the fast commences
Q: I made a niyyat for a nafil fast about 30min before sehri ends. Just prior to sehri ending, I decided that I should rather wait and make the niyyat for keeping fast before half the day, depending on how I felt. I was not going to eat during that time, until my niyyat was confirmed. Is it ok to change my niyyat for fasting afterwards, or is the first niyyat I made 30 minutes before sehri ended binding?