The answer to this question is now. Well not literally of course. I usually wait for dinner to enjoy the first sip of the day.
Rather the question relates to aging. And again the answer usually is, now. The economies and dynamics of the wine world compel producers to create wines that are ready to drink when they arrive on the shelves of your favorite wine shop.
Unfortunately, not all wine stores can be counted on to remove wines that are past their prime. And keeping a wine too long before opening can lead to disapointment as well.
I had an experience like that today.