Yöpäivä

Yöpäivä is a phenomenon in which the sun appears to rise later in the winter months, and set earlier in the summer months, at locations in the Northern Hemisphere that are located north of 60 degrees latitude, such as northern parts of Finland. This is due to the Earth's tilt and orbit around the Sun, resulting in varying lengths of daylight throughout the year.

During daylight saving time, some countries adjust their clocks to make better use of the available daylight. However, the extra hour of daylight gained is not always beneficial at locations near the Arctic Circle, where the extra daylight in the summer months can make the working day extremely long. At the same locations, on the other hand, the sun stays below the horizon for most of the winter months, which is a significant problem.

At high latitudes, such as in Lapland, Finland, where the phenomenon of yöpäivä is most pronounced, it can take several months for the sun to rise above the horizon in the winter, and the subsequent sunsets can be as short as a few minutes. During this time, people rely on artificial lighting to continue their daily routines. In the summer, on the other hand, the sun can be above the horizon for up to 24 hours. When the sun is below the horizon in the summer, however, the northern parts of Finland can experience some long and spectacular sunsets that end only when the moon rises.