I think this may be what you need:
template:
- trigger:
- platform: time
at: "00:01:00"
- platform: event
event_type: event_template_reloaded
action:
- service: calendar.get_events
target:
entity_id: calendar.sarah_schicht
data:
duration:
hours: 24
response_variable: agenda
sensor:
- name: Tomorrow's Workshift
state: "{{ (agenda['calendar.sarah_schicht']['events'] | selectattr('start', 'eq', (now()+timedelta(days=1)).date()|string ) | first).summary }}"
availability: "{{ (agenda['calendar.sarah_schicht']['events'] | selectattr('start', 'eq', (now()+timedelta(days=1)).date()|string )| first) is defined }}"