When is the best time to mediate?

Either first thing in the morning or right before bed. Doing it in the morning creates a peace for the rest of the day, and doing it before bed relaxes you and let’s you release the tension of the day.

To me I do it three times a day first in the morning after I wake up, to give me a peaceful mind.
Another time in the middle of my day to energise me and motivate me to continue my day with a smile and less stressful thoughts and actions.
Finally at night to rest my mind and sleep faster and better for another day ahead full of achievements.

I think there's not an answer that is right for everyone. It depends by your engagement. You can change them or not and meditate when you are free and when you feel better.
Howewer, the time is not the most important thing, you can do it in the morning, in the afternoon or in the evening. The most important thing is to begin, when you want, and being perseverant. You can always change the moment to meditate during the day.
Generally, if you want to reflect on what you have done during the day, meditate in the evening.
If you want to start right your day do it before you leave your house or when you wake up.
Remember it depends from you

I am personally meditating during my bedtime routine to avoid racing-mind when I go to sleep. Surprisingly for me it is working quite well 🙂