Currently, you must enter a period and then the dates of the contract are set. However, almost all contracts are for a listed start and end date and clients would like to be able to enter the dates and have the period calculated. It might be best to give the client a System Admin option as to how they want contracts calculated - by date ranges or by period. Additionally, currently only months and days are included, however in cases where a contract spans multiple years, there needs to be a year value on the Duration.