Main toolbar > Use Pivot Point Center (on Use Center flyout)
The Use Pivot Point Center button, available from the Use Center flyout, lets you enable rotation or scaling of one or more objects around their respective pivot points.
The axis icons show the centers that are currently being used.
Note that transformation center mode is set on a transform-by-transform basis, so select the transform before you select the center mode. If you do not want the constraints to change, turn on Customize menu > Preferences > General tab > Reference Coordinate System group > Constant.