Invoice Service Contract by calendar year

WillemL

We have service contracts with a duration of 3 years. We want first to invoice them until 31/12 of the current year and on 1/1 for the next year so we can group the service invoices for the same customer.

for a Service Contract starting date 2010-07-01 we want:
invoice period 1 = 2010-07-01..2010-12-31 ; invoice period 2 = 2011-01-01..2011-12-31 ; invoice period 3 = 2012-01-01..2012-12-31 ; invoice period 4 = 2013-01-01..2013-06-30

Any idea how we can do this?