The quickest way I can think of to show the creation time on a "Scheduled Task" entry would be to execute:
attrib -r -s -h %SystemRoot%\Tasks\Desktop.ini
ren %SystemRoot%\Tasks\Desktop.ini Desktop.ini.foo
This would open the %SystemRoot%\Tasks folder in a "normal" Explorer view and would let you review the times on the files stored there.
When you're done, rename and re-apply attributes to "desktop.ini" to make things normal again:
ren %SystemRoot%\Tasks\Desktop.ini.foo Desktop.ini
attrib +r +s +h %SystemRoot%\Tasks\Desktop.ini
It's a cheap trick, but it should show you the creation time on the task file for the task you're interested in.