When you renew an item, the new due date is calculated from the date you perform the renewal. The additional time is NOT added on to the end of the original loan period.
For example, if you check out an item with a 2-week loan period on January 2, 2014, the original due date is January 16, 2014 (2 weeks). If you renew that item on January 9, then the new due date will be January 23, 2014, that is, 2 weeks after the date of the renewal.
To get the maximum time on your loan, you should perform any renewals very close to the due date.
NOTE: If your Email address is in your patron record, you will receive an Email Library Reminder 3 days before your material is due.