The Last Enrollment criteria, which is stored in a date format is the only thing I can think of in the standard reporting that would be close to what you're looking for here. You can add this to a saved advanced search as a column to display.
But of course, that value can get updated/changed if a device gets re-enrolled at some later time. Even though the actual device record could be older, the "Last Enrollment" value would show something newer. Just something to keep in mind.
If the re-enrollment thing is a concern, then another option is to use the Jamf API to grab the initial_entry_date value, which stores, I believe, the devices original or "initial" enrollment date. The API value mentioned is in a simple YYYY-MM-DD format, with no time value. The initial_entry_date_epoch or initial_entry_date_utc values would both give you the option of seeing the time as well as the date if needed.
Hope that helps.
