When is SQL server installed

I have been asked may times how to find when a SQL server is installed. Mostly I told them to find the installation log. But, what I didn't realized is that you can find out by querying sys.syslogin database.To my surprise, quiet an easy statement. You can use

SELECT  createdate as Sql_Server_Install_Date, *
FROM    sys.syslogins
where   sid = 0x010100000000000512000000 

or

SELECT  createdate as Sql_Server_Install_Date
FROM    sys.syslogins
where  loginname = 'NT AUTHORITY\SYSTEM'

One of the above will do  as long as default language is English