Hopefully this helps - select your cell or the entire column: 
I've just tried many times to format the dates in the Annotation Editing Tracking Sheet in the desired way, and it's ridiculously hard, as the spreadsheet reformats every time and you have to go back and paste values only. Does it really matter how the date is formatted? Or, if it does, can someone inform me how to avoid this problem?
Hopefully this helps - select your cell or the entire column: