Here is a handy little SQL script to find out when your databases were last backed up on an MS SQL instance.
SELECT sdb.Name AS DatabaseName,
COALESCE(CONVERT(VARCHAR(12), MAX(bus.backup_finish_date), 101),'-') AS LastBackUpTime
FROM sys.sysdatabases sdb
LEFT OUTER JOIN msdb.dbo.backupset bus ON bus.database_name = sdb.name
GROUP BY sdb.Name
Enjoy! ;-)