In combination with the timeline it makes key words even more powerful.
You can pre-select images (create a view) by selection one or more keywords or, alternatively one or more albums. Now you see in the grid all images which have this keywords or albums assigned to it.
Now switch to the time line. You will see the timeline filled with the days one or more images were taken on.
You can select days in the timeline to see only a subset of images. Now you can select images and click on the checkboxes in the keyword view to add or remove the respective keyword.
Note: To avoid that you loose the preselection of images, the pre-selection by keyword is disabled while the timeline is displayed.