Demographic segment has a very useful feature for date fields - it is possible to add "relative date" criteria, for example "TODAY minus 3 days". This allows for example targeting of contacts created a number of weeks ago, etc.

This is not possible for Behavioral segments. Often it is desirable to apply a criteria on the Timestamp field but since relative dates are not supported, the functionality is very limited. For example, it is not possible to create criteria such as "2 months ago", "longer than 4 days ago", etc.