The New Testament defines 'evening' as sunset, which marks the end of the Sabbath (see Mark 1:32; Luke 4:40). However, in some parts of the earth (the Arctic regions) it is difficult (or impossible) to determine the Sabbath hours by the biblical sunset reckoning. That is due to the fact, that in these areas of the earth the sun either rises too early or to too late, and not at all during parts of the year.
Many Sabbath keepers living in the Arctic regions have adopted a policy of observing the Sabbath, when there are no sunsets, on the basis of the times recorded for the last visible sunset. In other words, they perpetuate the timing of the occurrence of last visible sunset until the next visible occurrence of sunset.
Other Sabbath keepers go by the sunset calendars just south of the Arctic region, during the period of the year when they have no sunsets.
In Scandinavian countries, some have set a broader definition for 'evening' to mean a diminishing of light. Hence, they build up the beginning and end of the Sabbath on when it begins to get darker. This is taken in lieu of the biblical sunset.
Lastly, some observe the Sabbath from 6 p.m. to 6 p.m., according to the equatorial sunset time .
The important thing to remember is that where sunset reckoning is available, then the Sabbath is to be observed on its basis. However, where the sunset reckoning is not possible, and in the absence of clear divine instructions on this matter, then any of the above common practices adopted by Sabbath keepers in regions with no observable sunsets would do; as long as a 24-hour period is set as holy and sacred on the seventh day of the week.
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