Why does the "Date Created" for the master database show such an old date (8 April 2003) in SQL Server 2008 R2? Why does the "Date Created" for the master database show such an old date?

I created the new instance today, not 2003.
This is just an educated guess mind you, but I would assume it is the date the new master database was created at Microsoft for SQL Server 2005.  

I checked SQL Server 2012, 2014 and 2016 and all have the exact same date/time.