There are different benefits in doing fitness in different time.
Morning: People doing fitness during morning will experience high metabolism and people who want to loss weight, these is the right time.
Good Afternoon: Do you want be Muscular? This is the right time for you to do. It also helps to boost testosterone.
Evening: For many of them, it is necessary to get rid stress which you gained during the day. So doing exercise during this time helps you to stay fit and positive.
It is not about what time you do, it is all about how much consistently you do and make it as a habit.