Get the time elapsed since the epoch using only std

In this example using only std, the standard library we fetch the time elapsed since the epoch (which is 1970 January 1 on Unix/Linux systems).

examples/epoch/src/main.rs

use std::time::{SystemTime, UNIX_EPOCH};
fn main() {
    let start = SystemTime::now();
    let since_the_epoch = start
        .duration_since(UNIX_EPOCH)
        .expect("Time went backwards");

    println!("start:           {start:?}", );
    println!("since_the_epoch: {since_the_epoch:?}");
    println!("as_nanos:        {}", since_the_epoch.as_nanos());
    println!("as_micros:       {}", since_the_epoch.as_micros());
    println!("as_millis:       {}", since_the_epoch.as_millis());
    println!("as_secs:         {}", since_the_epoch.as_secs());
    println!("as_secs_f32:     {}", since_the_epoch.as_secs_f32());
    println!("as_secs_f64:     {}", since_the_epoch.as_secs_f64());
}

Running on Linux this is the output:

$ cargo run -q

start:           SystemTime { tv_sec: 1707553108, tv_nsec: 951575643 }
since_the_epoch: 1707553108.951575643s
as_nanos:        1707553108951575643
as_micros:       1707553108951575
as_millis:       1707553108951
as_secs:         1707553108
as_secs_f32:     1707553200
as_secs_f64:     1707553108.9515758