let event = Event::new()
    .summary("test event")
    .description("here I have something really important to do")
    .starts(Utc::now())
    .class(Class::Confidential)
    .ends(Utc::now() + Duration::days(1))
    .append_property(Property::new("TEST", "FOOBAR")
            .add_parameter("IMPORTANCE", "very")
            .add_parameter("DUE", "tomorrow")
            .done())
    .done();

let bday = Event::new()
    .all_day(Utc.ymd(2020, 3, 15))
    .summary("My Birthday")
    .description(
r#"Hey, I'm gonna have a party
BYOB: Bring your own beer.
Hendrik"#
)
    .done();

let todo = Todo::new().summary("Buy some milk").done();


let mut calendar = Calendar::new();
calendar.push(event);
calendar.push(todo);
calendar.push(bday);