Time

The time resource can be used to track the global runtime of our App. Bevy also includes a Timer type which makes it easy to track how much time has passed during a series of events:

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .insert_resource(GreetTimer(Timer::from_seconds(2.0, TimerMode::Repeating)))
        .add_systems(Update, greet_people)
        .run();
}

#[derive(Resource)]
struct GreetTimer(Timer);

fn greet_people(time: Res<Time>, mut timer: ResMut<GreetTimer>) {
    if timer.0.tick(time.delta()).just_finished() {
        println!("beep");
    }
}