1. The "99" here actually refers to another "99". In ancient China, the summer solstice and the winter solstice were divided into nine sections, each with nine days, and every nine days was called "September 19th". They were named "September 19", "February 29" to "September 99", and were called "Summer 99" and "Winter 99" respectively. "99" usually refers to 99 in winter, that is, a period of time in a year when the temperature changes from low to cold and then gradually warms up, usually from the day of winter solstice to the end before and after the fright. Of course, it also refers to the last nine days of the ninth five-year plan.
2. "Sunny day" refers to sunny spring, and the word "sunny day" is used to describe spring.
3. The song1Sunny Day in 999 is an episode of the movie 1957.