Batch Invoice Posting is using a prior date

We set up the invoice batching with the same parameters every day and leave the invoice date in the Setup tab blank, we use quantity: packing slip, posting, late selection and print invoice are checked, we hit the select button, then the batch button to set the job to run in batch at 8 pm.  Every once in a while, and Friday is the most recent example, the batch posts the invoices with yesterday's date, we created the job on 8/2 set it up that same way we do every day, but it posted all the invoices with a date of 8/1.  Is there a problem with the batch invoice posting process?

Thank you,

Melissa