[Here](http://www.quantcast.com/superuser.com) are some usage statistics from Quantcast, which is used to track usage of SE sites (you'll see it as a tracking pixel when you check the loaded resources for each page).

![enter image description here][1]

Unfortunately, I haven't found how to get better resolution than *day*.

---

Using variants of *@DaveDuPlantis'* query, I created the following charts, that display the requested information in some more detail than the answers provided so far:

### All posts on SU by hour of day:

![enter image description here][2]

	select
	datepart(hour, Posts.CreationDate) Hour,
	count(Posts.Id) Questions
	from Posts
	group by 
	datepart(hour, Posts.CreationDate)
	order by Hour asc

### All posts of SU by hours of day and day of week:

![enter image description here][3]

	select
	datename(weekday, Posts.CreationDate) Weekday,
	datepart(hour, Posts.CreationDate) Hour,
	count(Posts.Id) Questions
	from Posts
	group by datename(weekday, Posts.CreationDate),
	datepart(hour, Posts.CreationDate)
	order by Weekday, Hour

<sup>I manually fixed the output to bring order to the weekdays</sup>

---

**Charts for 2011 only (using Oct 4 data set)**

The following are the same charts, but limited to posts created in 2011 only, by adding the following to the queries above:

    where YEAR(CreationDate) = 2011

----

![enter image description here][4]
![enter image description here][5]

Both charts for 2011 only are basically identical to those for the whole lifetime of the site. The absolute numbers are way down though, so it's not the domination of 2011 in the first charts that causes this: It's just that there was no shift in the times people post to the site.


  [1]: https://i.sstatic.net/HDUEa.png
  [2]: https://i.sstatic.net/2mSJd.png
  [3]: https://i.sstatic.net/OEkXG.png
  [4]: https://i.sstatic.net/SFEnL.png
  [5]: https://i.sstatic.net/mIKLu.png