What exactly is the status of time between Shkia and Tzeit Hakochavim on Friday? Is it fully considered to be Shabbos? If one accidentally did Melacha during that time, would they be chayav chatas? Likewise with the time after Shkia on Saturday.
Happy Purim and have a great Shabbos
The time period between Shkia and Tzeit Hakochavim is a twilight zone, in more ways than one. During this period according to a number of Rishonim, it is a safek if the new day has started yet or not, therfore we must refrain from doing melacha then. Aside from this we have to mekabel Shabbos before this period, and after that we were anyways mekabel Shabbos and can’t do melacha. Regarding a korban chatas, it isn’t clear that the person was mechalel Shabbos then. The same would apply to this time period after Shabbos,.