For me, it is 6pm till 2am!!! I usually avoid reaching office before 11am. From then, the usual meetings and mentoring stuff, code reviews, client calls! Ugh! But once the tide settled after 5.30 pm, I'm in my zone. There are time where I struggle to fix minor bug for hours, but the same can be fixed in minutes during my zone time.

when left alone with headphones and music blazing at 100%

I find my best programming is before 3 p.m. Sometimes letting a thread of interest go after that works too. When I join a PHP Coaching Institute in Jaipur for learning PHP, I select the 3 p.m. batches.

4am - 8am when the world is quiet

Around 3 PM to 11 PM

In the morning after my second cup of coffee :)

mostly depends on what I'm working on. If it's for my 9-5 job, I tend to be most productive after lunch (I'm SO NOT a morning person). I've "woke" up and have already gone over non-coding tasks by then. Also, as others have noted, distractions do not help with outputting good code. I hate when my boss (the CEO of the company) has a thought pop into his head and comes over to my desk to discuss it without regard to where my thought process is at!

if I'm working on my side project, usually after dinner I'm the most productive. I've detached (usually) myself from work issues, had a chance to unwind, then I'm good to go for the rest of the night :)

Usually in the morning. The more I am throughout the day, the more tired I am, and the quality of my code resembles this.

For me it is: all of the above

I spent last week trying to fix a bug with no results. Today I went to the offices for a code review.

While I was waiting for my boss I though I take another look at the code and then, something told me "look at the templates files". I did and there was the problem...

That's why I can't really tell for sure when do I write my best code. it can be anytime, anywhere.

i agrere with @mgiambanco my most productive time is when i'm interessted in the topic + what he said ;D and i'm an evening person. but i'm a freelancer so I don't have office hours if the customer does not force me :)

When I have zero distractions and am left alone with my work / music.

People holding general discussion in the office? Distraction

Meetings? Distraction

Wife cooking dinner / needs my help? Distraction

Sunday night and Ballers / Power / Ray Donovan / John Oliver / Random tv series on I want to watch? Don't even think about writing code

So between 530am and 8am is my best time, haha. I'm a morning person - have been for years; dream / think of the code as I sleep, write it as soon as I wake up.

My best code? Well, I always try to write the best code. But I feel best writing code in the time between afternoon and sometime past Midnight.

Night time is the best time of the day

Unfortunately, many companies do not understand that there are different people who have different productive times, so many companies still have "office hours". I really hope that will change with the introduction of UCC, bring-your-own-device and other new and inspiring working conditions.

Personally, I feel 11am - 3pm works best for me. In normal business hours, code reviews, meetings etc.. eat most of my time, leaving no time for creative thinking.