How to add time period in recurring invoice?

How to add time period in recurring invoice?

Is there a way to automatically add a time period in the line item on my invoice so the customer knows the invoice, for instance, is for last month?

Example... I send a monthly recurring invoice to my client on the 1st of every month for services rendered the past month. So on Oct 1 2014 I am billing them for Sept 2014. How can I indicate this dynamically in the line item?

Thanks