To retrieve the SQL Server Installation date, we have to check the login “NT Authority\System” creation date which gets created at the time of SQL Server installation.
-->> server installation date SELECT create_date FROM sys.server_principals WHERE name = 'NT AUTHORITY\SYSTEM';
SELECT create_date,* FROM sys.server_principals WHERE sid = 0x010100000000000512000000
SELECT create_date FROM sys.server_principals WHERE name = N'NT AUTHORITY\NETWORK SERVICE';
