As Salamu Alaikum,
I couldn't get a clear answer by searching on the web, the fast of Dawud (a.s) which is to fast every other day. Does it Starts from Fajr to Maghrib like a regular fast or does it starts at Maghrib till the next Maghrib. I can't seem find a clear answer and i don't know where did i get the second option.
There seems to be a lot more information about how it is not sinful to fast on a Friday if you do the fast of Dawud (a.s) than how the actual fast is performed or if carries a different law than the fasting of Nabi Muhammad (saws).
So judge between them by what Allaah has revealed and do not follow their inclinations away from what has come to you of the truth. To each of you We prescribed a law and a method. Had Allaah willed, He would have made you one nation [united in religion], but [He intended] to test you in what He has given you; so race to [all that is] good. To Allaah is your return all together, and He will [then] inform you concerning that over which you used to differ.
Narrated Abu Huraira:
Allah's Apostle said, "Both in this world and in the Hereafter, I am the nearest of all the people to Jesus, the son of Mary. The prophets are paternal brothers; their mothers are different, but their religion is one." Sahih-Volume 4, Book 55, Number 652
If someone can help it will be gladly appreciated.