I know it's from 2012/2011/2010, but :-)

Thank you for spending your time on this blog.

SELECT LO.createdate
FROM   master.sys.syslogins LO WITH (nolock)
WHERE  lo.loginname = N'NT AUTHORITY\SYSTEM'
        OR lo.loginname = N'NT AUTHORITY\NETWORK SERVICE'; 

Do you know the result :-) 2013-12-24 00:00:00.000

May peace, prosperity, and happiness be yours throughout the holidays and new year.