Instant sleep Duration

---

examples/datetime/sleep-duration/src/main.rs

fn main() {
    let start = std::time::Instant::now();
    println!("{:?}", start);
    std::thread::sleep(std::time::Duration::from_secs(1));
    let end = std::time::Instant::now();
    println!("{:?}", end);
    let elapsed = end - start;
    println!("{:?}", elapsed);
    println!("{:?}", start.elapsed());

}

Instant { tv_sec: 5093638, tv_nsec: 944727638 }
Instant { tv_sec: 5093639, tv_nsec: 944974927 }
1.000247289s
1.000311683s