How To Find Time Difference using Chrono library in Rust - time

Question

I have a Rust program where I want to do some simple benchmarking with start time and end time!
use chrono::{NaiveTime, Utc};
fn main() {
let start_time: NaiveTime = Utc::now().time();
let end_time: NaiveTime = Utc::now().time();
println!("Total time taken to run is {}", end_time - start_time);
}
The code above prints as:
Total time taken to run is PT520.532696S
I guess it is 520 seconds if I'm not wrong, but how can I convert that into minutes? Is there a better way?

Answer 1

A simple look to the doc give the answer:
use chrono::Utc;
fn main() {
let start_time = Utc::now().time();
let end_time = Utc::now().time();
let diff = end_time - start_time;
println!("Total time taken to run is {}", diff.num_minutes());
}
but be aware that it's not a good way to mesure time in a monotonic way, this code could show -5 minutes if user change the system date somehow. Also call time() remove the information of the date, and this is strange when you use chrono because generally you don't want to ignore the date so just remove time() call.

Answer 2

It seems the accepted answer has some potential flaws.
A potentially better way as recommended in the rust nursery
is the following:
use std::time::{Duration, Instant};
use std::thread;
fn expensive_function() {
thread::sleep(Duration::from_secs(1));
}
fn main() {
let start = Instant::now();
expensive_function();
let duration = start.elapsed();
println!("Time elapsed in expensive_function() is: {:?}", duration);
}