It sounds like you are placing fields from both tables on the same layout without using a portal to display fields from the related records. In that case the "oldest" related records will provide the data you see from the related fields unless you specify different settings in your relationship.
Open Manage | Database | Relationships
Double click the line connecting your two tables.
In the dialog box that pops up, you'll see you have check boxes labeled "sort records". The same side as the table that contains your date field, click this check box and specify a sort order that lists the date field and specifies a descending sort order.
Now click Ok to close each dialog box and test your layout to see if it now displays the record you want to see.
thank you! works fine