In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.
Q: The winter solstice (or hibernal solstice), also known as midwinter, is an astronomical phenomenon marking the day with the shortest period of daylight and the longest night of the year. It occurs when one of the Earth's poles has its maximum tilt away from the Sun. It happens twice yearly, once in each hemisphere. In the Northern Hemisphere this is the December solstice and in the Southern Hemisphere this is the June solstice.
A: 
when is the darkest day of the year