Answer:
As soft as silk, as white as milk, as bitter as gall, a thick green wall, and a green coat covers me all.
When the day after tomorrow is yesterday. Today will be as far from Wednesday. As today was from Wednesday. When the day before yesterday was tomorrow. What is the day after this day?
A time when they're green. A time when they're brown. But both of these times, cause me to frown. But just in between, for a very short while. They're perfect and yellow. And cause me to smile.
What has wings, but can not fly. Is enclosed, but can outside also lie. Can open itself up, or close itself away. Is the place of kings and queens and doggerel of every means. What is it upon which I stand? Which can lead us to different lands.
Who spends the day at the window, goes to the table for meals. And hides at night?
People take me on walks and I run and have fun. What am I?