$CreationDate
gives the date at which the particular release of the Wolfram Language kernel you are running was created.
Examples
Basic Examples (1)
Wolfram Research (1991), $CreationDate, Wolfram Language function, https://reference.wolfram.com/language/ref/$CreationDate.html (updated 2014).
Text
Wolfram Research (1991), $CreationDate, Wolfram Language function, https://reference.wolfram.com/language/ref/$CreationDate.html (updated 2014).
CMS
Wolfram Language. 1991. "$CreationDate." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/$CreationDate.html.
APA
Wolfram Language. (1991). $CreationDate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$CreationDate.html