There was a report that we had to put together for the servers that had re-started within the tenure and the probable reason for the restart.
Below query gives you the time the SQL Server Reatrted. This query assumes that the tempdb is created everytime the SQL Server restarts.
SELECT [Name] , CrDate as DateServerRebooted
WHERE dbid = 2
Now if you want to further when the SQL Server was stopped and the probable reason for the Server shutdown you have to go to the individual error logs and identify.