Question:
May Friday evening service be held before dark, when, due to climatic conditions and the geographic location of the camp, it is necessary to conduct the service when the hour set for the service is still in daylight?
Answer:
It is a positive commandment to add "from the profane to the holy," that is, to begin the Friday evening service a little early. The question is, however, how much it is permissible to anticipate the Friday evening service. The matter is fully discussed in the various codes.
Under war time conditions it is permissible to have the Friday evening service within an hour or two close to sunset.
While the principle of adding "from the profane to the holy" does not apply to early evening services during the week, we may also be lenient with regard to beginning them early, as is indeed the Ashkenazic minhag.