You can only enter a single date column, in which the invoice and the due date. However, you can add the date range manually, just customize the invoice template. I'll show you how:
From the Lists menu, select Templates.
Pick your invoice template from the list and open it.
Click Additional Customization to add information on the header.
Tick the Screen and Print checkbox beside Other.
Hit the OK button.
Once you've done, it automatically shows up on all invoices for all customers as long as you've added the field to the template. Then you can now create an invoice and manually add the date range in the Other column.