If a person is sick (bad cold, sinus infection etc.) what is the earliest he can say kriyas shema shel arvis in order to go to bed as soon as possible?
The earliest time for Krias Shma is halachic nightfall, at the emergence of three mid sized stars, known as Tzeis Hakochavim. This time varies from lace to place and time of year. myzmanim.com provides halachic times including nightfall, for all areas across the globe.