Bridges translate date data between partitions with different readiness status, allowing you to work on partitions separately. You will need them to serve as firewalls to prevent date pollution from partitions you have not yet updated and which are, therefore, using different date formats. You may also need bridges as interfaces to translate date data between partitions with permanent format differences.
Given this collection of applications or programs:
and the following selection of applications into a partition, you can see where you would need bridges at the partition boundaries. As you make each partition ready, burn the bridges and modify the code back to a direct interface.