For me, and very annoyingly, I find my urge to write is at its strongest when I climb into bed at night. Quite literally, as I pull back the sheets and climb in, new sentences and scenes for my WiP flood my mind. All day I avoid it because just opening up the document feels like a chore, and then bedtime hits and I'm raring to go. It's most infuriating.
Mine is apparently very early in the morning. Of course, that's when I wake up to have coffee-internet time. *sighs*
When I'm on the bus on the way to work and there'll be a frantic scrabble for a notebook or my phone so I can jote everything down because I just know I won't remember it all come home-time.
Mine comes right when I'm trying to fall asleep too. Sometimes I'm even struck with something that I think is brilliant, and i get a sudden adrenaline rush, making sleep impossible. I've also found mundane task like doing the dishes, jogging, walking etc very helpful in coming up with things. If i start running out of idea I'll go on a jog and try not to think about what I'm writing, that's when i'll fall into some new ideas.
I can get ideas basically any time and anywhere, especially when I'm in the bus/at university, but also at home, I noticed it's more during the day. And for writing, I write during the night, but just because right now I'm home for summer break so it's the only time I get to be alone and quiet.
I may have found a possible outlet for my bedtime creativity. I should be getting my hands on a laptop tomorrow. It's only a cheapo, and second-hand at that, but in that I'll only be using it as a WP it should do the job.
When I'm awake in my bed, morning or late night. This morning I slept in, but instead of sleeping I just daydreamed for two hours, getting lots and lots of ideas for things to develop in my current WIP which I'm editing atm. So I make sure I always have a notebook close to my bed.
Morning and night for me. First thing in the morning after I've had my coffee is usually when I write. But I feel creative in the evening too, around 7. I don't write then because everyone is home and distracting. But I use it to come up with some ideas for the next day.
At night. Which is annoying because once I hit the bed I'm exhausted, then all of a sudden this idea comes along, and I'm too tired to write it down, depending on my own memory. Either way, it's the ideas I get before bed which drive the story forward.
Creativity or inspiration hasn't struck me at all lately. My writing has gone dryer than Harrison Ford's humour.
Could really happen at any time of the day for me. It doesn't seem to have a preference, day/night/whatever.
I do most of my writing once the people in my house are asleep, and I get a lot of my ideas during my writing time, so it's night for me.