You can reorder a calendar by tapping "My Orders" in the Store tab, tapping the order, and then ordering it again. However, a calendar cannot be reordered if it starts more than 2 months before the current month.
Example: If it is currently May, you can reorder a calendar that starts in March, but not a calendar that starts in February.
Calendars that start more than 2 months before the current month cannot be reordered, so if you would like to order a calendar with the same photos, please create a new calendar from scratch.