DBCC DBINFO incorrect dbi_dbccLastKnownGood I'm trying to determine why DBCC DBINFO is returning different results than what is contained within the error log. Here's the setup:

Secondary Replica (read only access -- Asynchronous Commit AlwaysOn HA AG)


Job ran at at 02/05/2018 09:00:00 PM successfully, with a duration of 02:22:21
Only step in the job is DBCC CHECKDB(myDB)
When I run DBCC DBINFO('myDB') WITH TABLERESULTS I see dbi_dbccLastKnownGood  02/05/2018 00:00:40.113. This should be 02/05/2018 11:22 PM.
When I check the error log, I see 02/05/2018 11:22:09 PM DBCC CHECKDB(myDB) executed by myAccount found 0 errors and repaired 0 errors. Elapsed time : 2 hours 22 minutes 9 seconds. Internal database snapshot has split point LSN ... and first LSN ...


I decided to check the PRIMARY REPLICA where DBCC CHECKDB is also running (this is all set up by the vendor). 


Subplan ran at 02/05/2018 00:00:00 AM successfully, with a duration of 02:14:40
When I run DBCC DBINFO('myDB') WITH TABLERESULTS I see dbi_dbccLastKnownGood  02/05/2018 00:00:40.113 which is the same as the RoR but it should be 02/05/2018 02:15 AM.
When I check the error log, I see 02/05/2018 02:15:12 AM DBCC CHECKDB(myDB) WITH no_infomsgs exextued by myAccount found 0 error and repaired 0 errors. Elapsed time : 2 hours 14 minutes 40 seconds. Internal database snapshot has split point LSN ... and first LSN ...


I can't figure out where this DBCC DBINFO results is coming from, and why it doesn't match the SQL logs. I set up a job to send me an alert when the dbi_dbccLastKnownGood is > 24 hours.

Any ideas? Let me know if more information is needed.
READ ONLY REPLICA (Asynchronous AlwaysOn HA AG)

Like Erik pointed out, AG Replicas are currently read only so it can't update the values here. Additionally, if it did update the values it would just be overwritten the next time anything was updated on the primary and the log block sent to the secondary.

I decided to check the PRIMARY REPLICA where DBCC CHECKDB is also running 
•Subplan ran at 02/05/2018 00:00:00 AM successfully, with a duration of 02:14:40
•When I run DBCC DBINFO('myDB') WITH TABLERESULTS I see dbi_dbccLastKnownGood  02/05/2018 00:00:40.113 which is the same as the RoR but it should be 02/05/2018 02:15 AM

The job started 2:14:40 ago, which is the time of the last known good checkdb - that's true. You started it then, it ran for 2 hours and 14 minutes +/- some agent stuffs. The times look fine to me, it's not like the job ran for 5 seconds and shows a last good of 6 hours ago.
I believe the issue is you expect the CHECKDB to show the good value at the end of the run versus being updated when it was executed. That shouldn't be a problem.