The length of the red and green columns is the total amount of energy. One column is obviously higher than all columns in the previous long period, generally not less than half a year, and this column is many times or dozens of times higher than the previous period. This is the so-called days.

Then there is a column that is obviously higher than all the columns in the previous long time, generally not less than half a year. This column is one or several times lower than the previous one, and this column is called the amount of land.