Billing plan date should be same as invoice date as per factory calendar

Hi,

We have two contracts, one is having billing plan material and another is having no billing plan material of same customer.When we go for the billing, as because these having all the header fields same it should give one single invoice of those two contracts,but its giving two invoices means the invoice splits.I check it and found, due to different billing date the invoice splits.If we go for VF04 we can force the billing date as same,but they are is a one batch running for this invoice.My invoice date of two contracts is 22.06.2014 which is factory calendar date and billing plan date is 26.06.2014 which is contract start date.My client is asking that can we get billing plan date same as invoice date as per factory calendar in standard to get single invoice? Kindly suggest me where is the settings.

Thanks in Advance

Regards,

Braja