How can I sort groups by the date the individual was added to the group?
For a standard group there is no direct way to do that through the UI as the group(s) someone is in are stored in a single field.

If you are using smart groups, then you may be able to use the underlying criteria for the group to work out the joining order (eg, display and sort by membership join date if your smart group in based on a particular membership type). However that won't be ideal or even appropriate in many situations.