I prefer to play during the week, Monday to Friday between 12:00 - 18:00 GMT.
On weekends I do some extra work and I don't have much time to play.
In addition, to play certain tournaments, you must have your sleep up to date, and well rested, as there are tournaments that never seem to end.
So being rested is essential for the patience needed to play and do well.
Before, I preferred to play at dawn, but for a few years now I can't play that time anymore.
So for me the best days are: Monday, Tuesday, Wednesday, Thursday and Friday between 12:00 and 18:00 GMT.