It may not be what you are looking for, but if you have the same tasks (as in same name) I woul duse th ecompariosn feature (Under Project/ Compare Reports). This will give you all dates for both programmes, as well as a visual indicator of where the differences are. I have found this useful, especially for larger projects, where a visual can save an awful lot of time.

Quick note for clarification: the Compare Projects tool will only work on two copies of the same file. If the OP created a project and the other user created a separate project file, the Compare Projects tool won't work.