Usually, mornings are best for most of us. But not for everyone. And your personal fitness goals are an important consideration, whether fat loss or mass building, for examples. In the end, the best time for you is when you can get the workout in. Exercising at the “wrong” time is better than not exercising at all. Read this article for more information.
Muscle-building does not occur during exercise. Rather, exercise tears down muscles, which then rebuild and adapt during the post-exercise rest and recovery period. That is why, typically, specific muscle groups should not be worked on consecutive days. They should be allowed to recover for at least 48 hours, though 72 hours is generally best. The link below explains the scientific process.