2. Ultraviolet rays are much weaker than during the day and do little harm to the skin (suitable for beauty lovers).
As far as oxygen concentration is concerned, the highest oxygen content in a day is at night. As for running late at 7: 30, it doesn't matter. There is still a lot of oxygen at this time, which is very suitable for aerobic exercise such as running.
The bad thing is not to run too late, which may keep you awake at night!
Plus: actually, it's not that particular. As long as it is proper exercise, any time is suitable.