[sidney]

That is a peculiarity of fighting in the far north of Russia - in the summer time the days are long, and the nights are short, colloquially referred to as the "white nights". From personal experience, the "daylight" lasts until 1:30 - 2:00 Am (late May, early June, if I remember correctly). Under the circumstances, Obstlt. Trautloft proposed fighter patrols in the normally evening hours, which did achieve some successes against the partisan supplying aircraft in the summer of 1942. White victory tabs would refer to the "White night" victories.