Tai Chi is one of those martial arts that are hard to understand. You need to practice for a really long time and you have to take all the little advantages that are needed, which is not as easy as you may believe at first glance. The best time to practice Tai Chi is difficult to analyze because there is no strategy that is 100% viable for all individuals. However, we do have to consider some things.
For most people, the best time for Tai Chi is dawn. However, it is also worth mentioning that some teachers will tell you that the best possible time to practice is at the moment when you will wake up. For only a small number of people these two times are the same. Most will wake up at around 8 or 9 AM, with few waking up at dawn.
We have to consider your personal morning routine. For instance, do you need to simply brush your teeth before you do anything else? If so, do it. Practicing Tai Chi means you have to be really comfortable with yourself and your surroundings. At the same time, you have to dress appropriately. Being comfortable is something that counts a lot at the end of the day with basically all internal martial arts, including Tai Chi.
It has to be mentioned that no matter when you practice Tai Chi, your clothes and where you practice will have a huge influence on the experience. Obviously, the best thing you can do is to practice directly on the ground or on grass. This is not possible for a lot of people. You can practice in your own apartment but it is a very good idea to never wear non-rubber soled shoes. That is because anything that is insulated would stop you from gaining energy from the earth, which is so important in Tai Chi.
The last thing that we should mention about the best time for Tai Chi is the morning, but you also need to practice in the evening. You will need to do this every day for optimal results.