Clear as mud.
The Shortest Day of the Year
Winter solstice is the shortest day of the year. That means, it has the least amount of sun. In the northern hemisphere, it occurs on December 22nd each year. Oh, that is today! The farther you go North, the shorter the day will be. If you are near the north pole, there is no day. It is 24 hours of darkness at this time of year. There are a number of cultures that used to celebrate or still celebrate winter solstice. After all, each day will have more and more sunlight. Some refer to this day as a rebirth of the sun. It might be a better day to celebrate New Year's Eve because it is like the Sun's birthday. Unfortunately, when they were creating the calendar, it was easier to see full moons than to calculate the solstice. By the way, we can be even more specific about solstice. This year (2021), winter solstice will happen at 12:58AM on December 21st.
Meaning
Night and day is an idiom that shows a large difference between two things. It is often used to talk about people. It can be used to compare two (very different) people or to describe a transformation of one person. You can use it to compare someone to a previous version of herself. This phrase may be written as “the difference is night and day” or “it is like night and day.”
Example (compare): The difference between the twin boys is night and day.
Example (transformation): She has lost a lot of weight. She doesn’t even look like the same person. The difference is night and day.
Example (transformation): Since I got a new prescription for glasses, my ability to hit a baseball has been night and day.
Night and day can also be used metaphorically to describe a long period of time. It is like you are working all day and all night.
Example: The baby is crying night and day.
See Also: Apples to oranges, The other day, You made my day, Broken clock, The witching hour
For more English phrases and quotes, follow me on Facebook:
https://www.facebook.com/ESL-ToyBox-112152010890485
Reference
https://www.wweek.com/news/2019/01/02/why-doesnt-the-new-year-start-on-solstice/