Make google tts only say the time value inside states.calendar.mycalender.attributes.start_time

Configuration
1

How can I make my google tts script only say the time of the date/time stamp in states.calendar.mycalender.attributes:

alias: Goodmorning
sequence:
  - service: tts.google_translate_say
    entity_id: media_player.mini
    data:
      message: "Goodmorning, you have to work from {{ states.calendar.mycalender.attributes.start_time }} to {{ states.calendar.mycalender.attributes.end_time }} today"
mode: single

The two states.calendar.mycalender.attributes are formatted like this:

start_time: 2021-04-26 08:30:00
end_time: 2021-04-26 17:30:00
2

I ended up doing like this:

data:
      message: "Goodmorning, you have to work from {{as_timestamp(states.calendar.vagtkalender.attributes.start_time) |timestamp_custom('%H:%M') }} to...."