Last Modified Date

I want to see the last time changes were made by the owners of the dashboard.  We're looking for some time of version control so when we baseline the dashboard for audit purposes, we can determine if a re-review needs to be performed (i.e., there's meen changes to filters/sources, etc.) or if we can rely on the baseline already performed by audit (i.e., no changes since the last time a deep dive was performed).