This is a complex extension which indicates which cycle(s) and day(s) of cycle an activity is to occur within a care plan. extCyclesAndDays contains a cycle extension which is an integer which identifies which cycle(s) the activity is to occur within the care plan. The cycle extension then contains the extDaysOfCycle which contains a day extension. The day extension is an integer which identifies which day(s) of the cycle the activity is to occur. For example, for an activity that is on cycles 1, 2, 3, and 4 of the care plan and on day 1 of each of those cycles, there will be one extCyclesAndDays extension with four cycle extensions (for cycles 1, 2, 3, and 4). Each of the cycle extensions will have one extDaysOfCycle extension with one day extension (for day 1).