well in general for all humans, our adrenaline and hormones are highest in the morning when we wake up of course.
however in modern society with the use of stimulants, poor sleeping habits, electronic addiction, dysfunction eating patters, and our work schedules this can become complicated.
in the end i really beleive over the long term training at some point during the day, without being too close to bedtime is perfectly fine. i would NOT train at night if you have a normal sleep schedule