Whenever you can.
It’s hard enough to find the time to exercise when you have a busy lifestyle without then worrying about what time is best. The best time to exercise is when you have the most energy and/or you have the time. Then, to increase the chance of making it a habit do it at that time most days.
There are so many amazing benefits to moving and exercising regularly; it can reduce anxiety, help with weight management, is great for a healthy heart, keeps you mobile for longer, can make you happier, relieves stress, reduces risk of chronic diseases, prevents injuries, increases energy levels and so much more. The time of day you exercise has little to no impact on any of these, so never let it be a concern.
The easier you can get it into your routine the better.
Without telling you to suck eggs, if you are exercising early in the morning, be sure to go to bed earlier! Otherwise you’ll find you might not have the energy to exercise, be lacking in energy throughout the day, you may be more likely to snack and you won't find it sustainable.