When RentMaster starts up, it automatically generates new rent periods if the date has advanced past the last rent period in the database.
If someone advances their computer date a long way into the future, and for some reason quite a few people actually do this, then when they start RentMaster, it will generate a whole load of new rent periods, which dramatically increases the total rent due for the tenant. When they return their computers date back to its correct date again, the damage is already done, and the total balance due is still a large number.
What RentMaster will do now, is it will ignore all rent periods where the period start date is ahead of the current computers date. The exception is when the tenant only has one rent period, which is the case when a new tenant is created with a start date in the future. All tenants need at least one rent period.