Team Services | TFS 2017 | TFS 2015 | TFS 2013
Your sprint planning and tracking tools automatically consider days off when calculating capacity and sprint burndown. Leave those days of the week that your team doesn't work unchecked in your team's Settings, Working days page.
If you're not a team administrator, get added as one. Only team and project admins can change team settings.
Other quickly configurable options you can make: