View the original community article here
Last tested: Dec 26, 2017
This is currently a feature request! Plus one the request in Pendo here.
If you have access to Looker's logs, you can try looking for this in the logs. If you grep for
UPDATE and then for
= X where X is the dashboard ID, then you may find lines that show when the dashboard was changed. Of course, you'd have to do this across each day's logs.