@freepeoplesfreepress dusk and dawn are the ideal times because .. you want the sun to have just start to split the F-layer but before the d-layer forms...
That said 10m performs very well mid day where the d-layer has formed (so absorbs a bit but 10m gets through it best), and the f-layer is fully formed.
Usually when its completely night time you wont get much of any activity on 10m because the F layer is not charged properly to reflect it.