Trying to determine when my water fast technically began

On Thursday 4/9, I finished a meal at 6pm and took a time-release 1g vitamin C at around 8pm. On Friday morning at around 7am, I took another vitamin C. Then as the day went on, I had no hunger and just decided to start a water fast.

I have read a lot about water-fasting and had dabbled in it before, so it wasn't as if I was totally unprepared. I know there are specific preparations that some people feel are necessary (enemas, two days of raw vegan, etc), but I would not have done any of those things even had I been planning on fasting, so please ignore my lack of prepping.

So anyway, since that time-release C on Friday morning, I have consumed nothing but water. I have tried to research how long the time-release process is, but have not been able to confirm whether it is 6 or 8 hours. But regardless of when the last dose of C was delivered to my system, when can I consider my Water Fast having actually started?

Since I took the two C's so early in my fast, long before the cleansing process started, can I consider the culmination of Thursday's meal as the start of my fast? Or did my fast start when I took the second C that Friday morning? OR did my fast start when the final dose of C was delivered to my system at either 1pm or 3pm on Friday?

Please do not respond if you think taking vitamins is acceptable during water fasting. Only reply if you agree that vitamins hinder the healing/cleansing process. Also, I do not know what I ate for dinner Thursday, but I know that the last part of the meal was one cup of Bob's Red Mill flaxseed meal.