Assalamualaikum. I unknowingly(my clock was running slow) had food after the Fajr azan and stopped as soon as I realised my mistake.Will my fast be valid? should I redo my fast?

Assalamualaikum Imam Sahib. Last night I got up for Sehri at 5 am and was having my food when a glance at my computer screen showed the time as 7 am(the fajr azan is at 6:31 am). I realised that the clock that I followed was running late by two hours. It was dark outside and I could not make out what the time was.I forsook my food immediately as it was and continued with the fast. I had set my intention for fast in advance. Will my fast be valid. Should I repeat my fast? Please advice. Jazakallah Khair.