Yes, DBA_CONSTRAINTS.LAST_CHANGE does say when the constraint was last enabled or disabled, and there is no persistent record of when the constraint was created. Like columns, constraints are not regarded as independent objects. Rather, adding a constraint is seen as a change to the table and is reflected in DBA_OBJECTS.LAST_DDL_TIME for the table.

Is there anyway to tell when a constraint was created? There doesn't appear to be any details kept on this like the other objects (tables, indexes, etc. which can be found in the DBA_OBJECTS view for example). If not, are you aware of any reason why this detail isn't kept. There is a column called LAST_CHANGE in DBA_CONSTRAINTS, but I am under the impression that this shows the last time the constraint was enabled or disabled.