What is your best time for workouts?

I prefer earning morning hours when the air is fresh.  I often choose a place with a lot of greenery around so that fresh oxygen is available in plenty.  As the day progresses it gets polluted. I mainly practice  Yoga and it involves a lot of breathing exercises.  So availability of  clean unpolluted air is very important to get the maximum benefit out of it. Sometimes when I am in a hurry I usually go for a walk and that keeps me fit and fine.

What time do you choose to do your exercise and what form of exercise you follow?