When a person's record has retention information and the Retention Start Date is set to begin from their date of birth, changing the date of birth recalculates the retention dates on the retention screen based on the new date of birth. However, the back-end table doesn't update these dates. As a result, the Retain Until Date shown on the Person Summary screen remains the same as it was before the date of birth change.
This is a bug, and we'll roll out a fix in a future release.
In the meantime, you can use this workaround: if the date of birth changes, remove the file retention criteria and re-add it.