I don’t know if i just don’t the correct way to use it. Or it maybe a bug?
But have made a template sensor with the following satement
{{ (as_timestamp(states.sensor.calc_leave_time.state) - as_timestamp(now())) | int }}
and that gives me a number at start up, but it never updates when the time changes.
Only when again restart hass it will update.
Bug or wrong configuration?