How do you find the last time a database was accessed?

To expand on James Allen’s answer:

SELECT d.name,
last_user_seek = MAX(last_user_seek),
last_user_scan = MAX(last_user_scan),
last_user_lookup = MAX(last_user_lookup),
last_user_update = MAX(last_user_update)
FROM sys.dm_db_index_usage_stats AS i
JOIN sys.databases AS d ON i.database_id=d.database_id
GROUP BY d.name

Use this modified version if you don’t want results per database context and wish to include the database name at the beginning of the result set.