I created a SEDE query for the distribution of the creation dates of questions and answers by time of day (in UTC): At time of writing, the result looks like this

The data comes from the entire time TeX StackExchange existed until 2018-08-01, 19:20.
The following graph only analyzes posts from 2017 (SEDE query):

As far as I can tell this is not possible for votes: While votes are accessible using the Data Explorer, the time is considered private information.
Since this is a LaTeX forum, one can also plot the data with LaTeX means.
\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots,filecontents}
\begin{filecontents*}{allquestions.csv}
Hour,Name,Activity
0,Question,0.02742403306
1,Question,0.02445506715
2,Question,0.02222056242
3,Question,0.0215981377
4,Question,0.01952546339
5,Question,0.0200545244
6,Question,0.02334092691
7,Question,0.03000087139
8,Question,0.04025843074
9,Question,0.04803873971
10,Question,0.05047242036
11,Question,0.05041017788
12,Question,0.0528002888
13,Question,0.05857639018
14,Question,0.06190013817
15,Question,0.06244787192
16,Question,0.06130883469
17,Question,0.05616138228
18,Question,0.05274427058
19,Question,0.05022345047
20,Question,0.04956990452
21,Question,0.04505732531
22,Question,0.03954886656
23,Question,0.0318619213
\end{filecontents*}
\begin{filecontents*}{allanswers.csv}
Hour,Name,Activity
0,Answer,0.02900122291
1,Answer,0.02304429242
2,Answer,0.02030228914
3,Answer,0.01757939389
4,Answer,0.01709691596
5,Answer,0.01880708526
6,Answer,0.02365097259
7,Answer,0.03209194787
8,Answer,0.04143100087
9,Answer,0.04653284671
10,Answer,0.04889746627
11,Answer,0.04756945771
12,Answer,0.05039267015
13,Answer,0.05562827225
14,Answer,0.05880020636
15,Answer,0.05993235754
16,Answer,0.05978427026
17,Answer,0.05552795505
18,Answer,0.05219360262
19,Answer,0.05225570374
20,Answer,0.05434803378
21,Answer,0.05271429663
22,Answer,0.04531948637
23,Answer,0.03709825352
\end{filecontents*}
\pgfplotsset{compat=1.16}
\begin{document}
\pgfplotstableread[col sep=comma]{allquestions.csv}\qtable
\pgfplotstableread[col sep=comma]{allanswers.csv}\atable
\begin{tikzpicture}
\begin{axis}[
width = 0.85*\textwidth,
ymin=0,
height = 8cm,xmax=24,xmin=0,
ylabel = {activity},xlabel={time of day},
legend cell align=left,
legend style={
at={(1,1.05)},
anchor=south east,
column sep=1ex
}
]
\addplot table[x=Hour ,y=Activity,col sep=comma]{\qtable};
\addlegendentry{questions}
\addplot table[x=Hour ,y=Activity,col sep=comma]{\atable};
\addlegendentry{answers}
\end{axis}
\end{tikzpicture}
\end{document}

Here is the plot for the 2017 data. To produce it,
follow this
link and download the file "QueryResults.csv"
remove the obnoxious <cr>
with dos2unix and remove all apostrophes in that file
Then you will be able to compile
\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\begin{document}
\pgfplotstableread[col sep=comma]{QueryResults.csv}\datatable
\begin{tikzpicture}
\begin{axis}[
width = 0.85*\textwidth,
ymin=0,
height = 8cm,xmax=24,xmin=0,
ylabel = {activity},xlabel={time of day},
legend cell align=left,
legend style={
at={(1,1.05)},
anchor=south east,
column sep=1ex
},
]
\addplot table[x=Hour ,y=Activity,col sep=comma,
skip coords between index={24}{49}]{\datatable};
\addlegendentry{questions}
\addplot table[x=Hour ,y=Activity,col sep=comma,
skip coords between index={0}{24}]{\datatable};
\addlegendentry{answers}
\end{axis}
\end{tikzpicture}
\end{document}
to get
