Richie Lee has a script to check the last known CHECKDB run date:
One of the most important duties of a DBA is to ensure that CHECKDB is run frequently to ensure that the database is both logically and physically correct. So when inheriting an instance of SQL, it’s usually a good idea to check when the last CHECKDB was last run. And ironically enough, it is actually quite difficult to get this information quickly, especially if you have a lot of databases that you need to check. The obvious way is to run DBCC DBINFO against the specific database. This returns more than just the last time CHECKDB was run, and it is not especially clear which row returned tells us the last CHECKDB (FYI the Field is “dbi_dbccLastKnownGood”.)
It’s a bit of a shame that this information isn’t made available in an easily-queryable DMV.