What is considered best: to exercise in the morning or at night?

Generally AM is best: First of all, exercise at anytime is great. If given the option, i recommend morning exercise for a number of reasons: 1) it is done and you can't put it off, 2) you get the benefit of the adrenaline (a stimulant) during the day, and 3) you will likely sleep better that night by not having adrenaline peak during the night.

Depends: Probably the best time is when you can and will do it. If you exercise too late in the day, it may make it hard for you to get to sleep. Try different times, and see what works best for you: in terms of how you feel through the rest of the day, how you sleep, your energy level, etc.