It is not the time of day as much as the effort and results....  Walking is one of the most natural, and easy exercises...  Unless you have some physical handicap of course... 

I try to hike at least once a week, usually on Sunday afternoons, is a State Park near by... But like you often other things come up, so we must learn to take what ever time is available...  As long as you are doing it, is what really counts...  Just think of all those who either plan to start or start and do not continue their walks... 

So like you,  I was taking advantage of the opportunity....  The weather has been so what unpleasant lately, but yesterday was  Sunny almost 60F...    I was off early {15:00 or 3 PM} and the park is on the way home, I keep my hiking sticks in the SUV, w. a back pack including water and a first aid kit...  Just called my dear wife and said I was going to take a hike...  The good kind...   Did Four miles in a little over an hour, some is strenuous on one of the trails, but it felt good!!

So keep up your efforts, see ya.. K