Ensure that the oldest creation date is preserved when deduping
Normally when you go to merge 2 contacts CiviCRM will by default suggest to merging a higher cid into a lower cid which will mean that the create date on the merged records will be correct. However if you flip it so your merging a lower cid into a higher cid for whatever reason, it is likely you may find that the create date is now wrong because there may have been activites or other items created on the lower cid before the higher cid came around.
thoughts @eileen