There was a mass update performed on a specific date that duplicated over 5000 customer records. It also updated the contacts tied to those records so I cannot delete the new record without manually updating all the individual contacts. Is there a way to delete all customers created from a specific date?

I have tried individually merging some of these but the new created accounts pulled contacts from multiple customers causing me to individually update contact before I can delete or merge an account.

This is going to be a huge manual time sucking process if i cannot somehow un-do this update. The "context" of the update is SOAP Web Services.