Is there a reason why rehire date does not have its own date type? Seems rather odd to have two different dates tied to the same date type. Think in terms of reporting - how will you differentiate? Of course, there is option to write logic to compare both dates and the one that is more recent will be the rehire date but you can avoid doing that.
I have 2 recommendations for you -
1. Create a seperate date type for rehire date.
2. Use DAR12 in your dynamic action - It is very unlikely that a person will have 12 dates on a single record. Using DAR12 will ensure the date type and date will default in the last spot and upon saving, it'll adjust.
Hope this helps.
Donnie