Q: I did not have an intention to fast the Ramadaan fast today so I did not wake up for sehri but I did not eat anything for the day. During the course of the day my intention is to fast. Can I still fast or not?
A: If you had not eaten anything since sehri time, then you are allowed to make an intention and start fasting. However, the intention must be made at one hour before zawaal. Furthermore, when making the intention, intend that you are fasting from subuh saadiq (i.e. dawn)
Find out from your local musjid what time is zawaal in your area. If you had made the intention one hour before, your fast will be valid.
Mufti Siraj Desai