Service Plan

Hi Experts

we are working on service contract with service plan item.we are creating service plans for every three months.At the time of creating service contract with Plan item start of interval is showing creation of contract date.Once i save the contract start of interval changing to 400+ years(ex-2010 to 2452).Due to this it is creating nearly 1800 service orders insted of four(ex-yrs 442 X 4).we are using standard date profile and standard item category(SPLA) only.what could be the reason for changing start of interval. Please help us on this issue.

Regards

Sreedhar

Please anyone suggest reason for this issue