How to automatically find when SQL Server (2008) was last started?

There are multiple way to find this information. However I use one of the below options:

Option 1:
Find this information from SQL Server Error Log.

Option 2:
Find when tempdb is created. A simple command as sp_helpdb 'tempdb' will give this information. We can conclude that this time/date (when tempdb was created) is the last start-up time of SQL Server.

Option 3: 

Please use below code:

SELECT
sqlserver_start_time
from
sys.dm_os_sys_info

However please note that this feature is available only from SQL Server 2008 onwards.