I hope you will get a lot of answers and for a correct evaluation you should take into account where on earth these people live : I live in the middle between Asia ( plus six hours ) and the United States ( minus six hours ), so what I see is a lot of opponents from one side or the other on mornings and evenings, it is absolutely notable ! ( You have to figure this out yourselves... ! )
What time do you play your best chess?

On second thoughts : " What time do you play best ? " depends on your own strenght, as you say so, but also on the results you can measure.
I do not know exactly, but my score is higher with Asian players compared to the Americans, and they are persistent in playing series of bullet and blitz games.

I Play better when I am fully awake (any time of the day)
but to answer the question, I tend to do better in first rounds of tournaments (mornings) because I am very nervous, which helps me concentrate more. By evenings, I grew very tired.

Usually in the evening, but definitely before I'm too tired by after I've gotten over my morning grogginess, probably after exercise.
My very best chess, of course, is generally played at the times when I am winning, unless my opponent is just a screw up.

hmmm... woke up this morning at about 8am, and thrashed the computer. Interesting because I had to fight for a draw yesterday at midday. So it seems I play best when I'm tired!

My best time is between 1 am - 3 am.
I am a vampire, not sure what in Likhit's excuse.
dude,stop acting.Well,actually King is my partner and we do the chess thing together.

I'm freshest in the morning and rarin' to go. Start to slow down after 1900. Could have something to do with getting up at 0415 though ;-)
I Play better when I am fully awake (any time of the day)
but to answer the question, I tend to do better in first rounds of tournaments (mornings) because I am very nervous, which helps me concentrate more. By evenings, I grew very tired.
i play better in the middle of the tournament. recently, at a rating tournament, i lost my first 2 and last games, but achieved a rating of 1348 because i did well in the middle! :D ( all 3 players were rated, i got 9 rated players in total )
I've been testing myself over the years...I always think good night's sleep will give my brain a rest and ill be fresh in the morning..but I'm usually groggy and my chess is not so great. For some reason I play good chess from around 7 pm to maybe 12 am. My mind is active..In fact I had my best win OTB, and it was in the evening! Ended at 10:30 I think. I only play well in the morning when I have some coffee and something minimal to eat (something not too sugary, etc.) What time do you play best? In the morning, afternoon, or evening?