The sun rises and sets at different points of the horizon throughout the year, which is what causes days to become longer or shorter. This process slows down during mid-summer and mid-winter, and for a few short days, the sun appears to rise and set at the same points of the horizon, causing most people during antiquity to believe that the laws of nature had been suspended for a short period of time. It was commonly believed that during this short window, human beings and the supernatural could interact with one another
Gnomes are said to live in and around gardens, and to come out at night to work on said gardens. If the gnome is caught in daylight, they turn to stone, in whatever position they were caught in. This is why gnomes are placed in gardens in a variety of positions. The idea is that they come out every night and are frozen the next morning during sunrise in whatever position they were in when the light from the sun touched them