Question: Today, Tuesday, is the fourth day of my fasting for the Six Days of Shawwaal. This morning, I woke up annoyed and looked at the clock; it was 04:15 A.M. The Athaan (call to Prayer) of Fajr (Dawn) Prayer is announced at 04:35 A.M. So I smoked a cigarette and drank some water and then went to the Masjid (mosque). I found someone sleeping there, so I woke him up to illuminate the Masjid in preparation for Fajr Prayer. The man told me that they had offered Fajr Prayer at its due time, i.e. at 4:55 A.M. I looked at my watch and saw that it was 5:30 A.M. And not 4:30 A.M. As I had first thought. However, I continued my Sawm (Fast). Can you tell me the ruling on this? May Allaah forgive you and me!
Answer: If the reality is as you mentioned, your Sawm on that day is not counted as valid by Sharee‘ah (Islaamic law). Your Sawm was spoiled because you drank some water after Fajr Prayer in error, neglecting to find out the exact time... read more here.