I use PBS postage with delivery confirmation.  Since you have to choose a mailing date I always choose the next day because I put it a rural mailbox for pickup.  He can get here anywhere from 9:00 until noon with the delivery/pickup.  If I put the next day's date on the label and happen to get it in the box before today's delivery will it still work OK?  Example:  Today is the 21st.  If I date the package the 22nd, and it gets picked up today, is it still OK.  I know you can't mail it later than the postage date, but is early doable?

Early is always acceptable. You shouldn't have any problems sending it out a day early.

Thanks, Melanie.  I often don't get to my email in the mornings until 10:00-10:30.  I never know if the mailman has been here or not and mail the next day just to be safe.  Maybe now I can get books in the mail a day earlier rather than hold them.