Simply should have the option to set up a vendor with Payment Terms of Month Following.

Example: An invoice dated for April 8th, that is not due until the 15th of the following month (May 15th). Instead of having to calculate the specific number of days in between, Simply should have a "Month Following" option with a box with the specific date to be entered into. About 50% of the invoice I receive have Month Following terms, so it would be nice to not have to either calculated the days in between or purposely enter the invoice date wrong to accommodate.