A workout regimen is typically most successful if it is performed on a regular schedule.
This is what people struggle with the most. Some people just have a hard time figuring out a good time to work out.
From a physical stand point a good time to work out is after you have been awake and moving around for two hours and have had a good meal.
This is not always convenient since this would be hard to do before work.
Morning workouts work for some people, but take care if you have back issues.
While you sleep, the discs in your back accumulate fluid, once you wake up and move around for an hour or so they return to their regular size. If you perform too much bending right after awaking, you could cause back pain that could lead to a herniated disc.
Another option is to work out during your lunch hour.
This is good because you will be more focused for the second half of your day.
The downside is being sweaty; this can be addressed if you have access to showers.
The last option is after work. Some people struggle with working out after work because they are tired and just want to go home.
This is where having a training partner can help with motivation. If you do work out later in the day, it is best to do so at least two hours before bed as to not adversely affect your sleep.
One thing to keep in mind is that you tend to learn and perform better mentally after a workout.
This can be useful if you have mentally challenging work or you are a student preparing for a big test. The best time to work out is when it works best for you while avoiding too early or too late times of the day.