22.214.171.124.2 New Instance Dates
Some recurrence patterns are sliding. In such cases, the recurrence pattern does not specify the absolute date of each occurrence. Rather, the recurrence pattern specifies a date that is relative to the completion date of the prior instance. The client computes the date of the new instance accordingly.
Having determined from the recurrence pattern the appropriate date for a new instance, the client determines and sets the values for the start date and due date properties of the new instance. The new values of these properties are determined by combining the values of these properties from the prior instance with the newly calculated instance date, as follows: If the prior instance does not have a start date, the new instance does not have a start date, and the new due date is the newly calculated instance date. Otherwise, the new start date is the newly calculated instance date and the new instance and the new due date is the sum of the new start date and the difference between the old due date and the old start date. In other words, new due date = new start date + (old due date - old start date).
Finally, the client sets the reminder properties of the new instance, as specified in [MS-OXORMDR]. In particular, the client sets the PidLidReminderSet property ([MS-OXORMDR] section 126.96.36.199) of the new instance to 0x01 if the reminder time has not already passed and (a) the PidLidReminderSet property of the prior instance is 0x01, or (b) the PidLidTaskResetReminder property (section 188.8.131.52.6) of the prior instance is 0x01. If the reminder time has already passed but either condition (a) or (b) applies, the client sets PidLidTaskResetReminder to 0x01 so that future instances can continue to follow the same logic.