Because Dashboards are collections of Reports, you can edit a Report and then realize the change on Dashboards that contain that Report. Given the question, it sounds like you might be building a Gainsight CS report, @MelissaC , on the Activity Timeline object.

If so, you should find the Report in Report builder and open it for editing. Then add the Activity Date field, which represents the recorded date of that Timeline entry. (And note that Activity Date can entered manually by end users. That can often differ from Created Date, which cannot be entered/edited by end users and represents the timestamp of when the Timeline entry was created regardless of the Activity Date that was entered.)

More here:

https://support.gainsight.com/Gainsight_NXT/Reports_and_Dashboards/User_Guides/01_Report_List_View_and_Settings#Introduction