This is the proper process. The system will first assume you are voiding against all of the original dates. However, when you (as MANY people do) need to void a check several month, even a year later, you need to change the posting date. You should also change the date of the transaction.
The issue you must recognize is, however, that these checks will show as un-cleared in bank reconciliations from the date issued until the date posted. But then again, you should have already reconciled those months and carried the checks forward as un-cleared.