Most people think you need a nice and bright day to take pictures. The above image shows what it looks like to take pictures during the harshest lighting conditions directly under the sun.
I have clients contact me on the day of their wedding worried that it's a cloudy day and that their pictures won't come out well.
My response is always the same, "You are in luck, your pictures will come out even better".
"...if your photo sessions is on a cloudy day then you are in luck."
Here is another example of pictures taken on a sunny day directly under the sun. If a photo shoot is at a park it's really hard to find a workaround. However, if it's a location with a lot of trees and buildings it's possible to find some shade.
So when is the best time?
Best time to take pictures is about an hour before sunset. Summer time it would be as late as 7:30PM (and a bit earlier depending on the locaton) and in the winter time around 4PM because of daylight lavings.