How can we improve WHMCS?

We have clients spread across the UK & US, the system already caters for their local currently & telephone number but we have a huge issue with date format for US clients

We began as a UK Host, so date format is DD/MM/YYYY but US are thinking renewal dates are: MM/DD/YYYY which leads to huge confusion for them.

It would simply be easier to detect the billing addresss County, and set a date format based on it