Spring '16 [Release Notes](http://docs.releasenotes.salesforce.com/en-us/spring16/release-notes/rn_apex_new_classes_methods.htm#rn_apex_new_classes_methods_changed_classes) a new system method supporting this:

> `Test.setCreatedDate(recordId, createdDatetime)`
> 
> Sets CreatedDate for a test-context sObject.

This will definitely complement the loadData() and deserialize() techniques.

    Account account = new Account(Name = 'Test');
    insert account;
    
    Datetime yesterday = Datetime.now().addDays(-1);
    Test.setCreatedDate(account.Id, yesterday);