Tanzania and Kenya being located close to the equator, there are few variations during the year in the hours of sunrise and sunset. The sun rises around six o'clock in the morning and sets around six o'clock in the evening. Therefore seven o'clock in the morning is the first hour of the day, and seven o'clock in the evening is the first hour of the night. We may thus consider that there is a six hour shift between Western time and "Swahili" time. However, while time is read and even written according to the Swahili system, the clocks are always set Western fashion. Therefore, one always has to add or substract mentally six hours to read time correctly.
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