Guide - add a holiday to a BACnet schedule

Goal: on one date, the controller follows a different value than the weekly schedule, by adding an exception to a Schedule object.

Before you start

• The Schedule object is imported. It appears as a sensor that shows the value the schedule currently commands.
• Each BACnet device is its own entry, titled with the device name, under Settings → Devices & Services → BACnet IP; the schedule sensor is on the device page of your device.
• You know the entity ID of that sensor, for example sensor.ddc_heating_schedule.
• Read Schedules: the exception schedule is always replaced as a whole.

Steps

1. Go to Developer tools → Actions and run bacnet.read_schedule on the schedule sensor. This shows what your controller returns, including the existing exception_schedule. Developer tools shows the response itself. response_variable is only needed in an automation or script.

   action: bacnet.read_schedule
   target:
     entity_id: sensor.ddc_heating_schedule
   

   

2. Copy the existing exceptions. You must pass them again, or the write fails.
3. Run bacnet.write_schedule with the full list: the existing exceptions and the new one. The value is written in the datatype of the schedule itself. priority runs from 1 to 16; lower wins. After the write, the schedule is read back. You should see no error. Run bacnet.read_schedule again to confirm the exception is there.

   action: bacnet.write_schedule
   target:
     entity_id: sensor.ddc_heating_schedule
   data:
     exception_schedule:
       # ...plus every existing exception you want to keep
       - period: { date: "2026-12-25" }
         priority: 10
         time_values:
           - { time: "00:00:00", value: 16 }
   

If it doesn't work

• The action fails and lists exceptions: the write would remove exceptions the device has. Pass the full list, or set allow_removal: true if removing them is what you want.
• The action fails after the write: the device rejected the change or stored something different.
• The dates look different when you read them back: dates are returned with raw BACnet numbers (month 13 and 14 mean odd and even months, day 32 the last day of the month).

More detail: Schedules and bacnet.write_schedule. An automatic version: Calendar events as schedule exceptions.