There are many ways you can use time, and can add them to about all the Google Earth features ie placemarkers, image overlays. The easiest one to do is the placemarker and I do this in cemeteries, especially if it's a project where you map out the whole cemetery. It makes for a great animation as you can see how the cemetery is populated.
The fastest way to do this is to document your placemarkers in Excel and then convert it to KML. I will cover this in some detail in a future post but here is an example of the spreadsheet I use.
This is my first attempt adding video to this blog. Below should be a animation of what adding time looks like to placemarkers in a cemetery.