Please paste in the YAML above as it appears in the editor, correctly formatted (see here).
Next, copy/paste the following into the Template editor and copy/paste into here what it returns:
{{ states('sensor.skiboard_next_alarm') }}
{{ states('sensor.skiboard_next_alarm')|as_timestamp }}
{{ as_timestamp(states.sensor.skiboard_next_alarm.state) - 60 * 5 }}