Duration and Calculation
Measure the elapsed time between two code sections
Measures time::Instant::elapsed
since time::Instant::now
.
Calling time::Instant::elapsed
returns a time::Duration
that we print at the end of the example.
This method will not mutate or reset the time::Instant
object.
Perform checked date and time calculations
Calculates and displays the date and time two weeks from now using
DateTime::checked_add_signed
and the date of the day before that using
DateTime::checked_sub_signed
. The methods return None if the date and time
cannot be calculated.
Escape sequences that are available for the
DateTime::format
can be found at chrono::format::strftime
.
use chrono::{DateTime, Duration, Utc};
fn day_earlier(date_time: DateTime<Utc>) -> Option<DateTime<Utc>> {
date_time.checked_sub_signed(Duration::days(1))
}
fn main() {
let now = Utc::now();
println!("{}", now);
let almost_three_weeks_from_now = now.checked_add_signed(Duration::weeks(2))
.and_then(|in_2weeks| in_2weeks.checked_add_signed(Duration::weeks(1)))
.and_then(day_earlier);
match almost_three_weeks_from_now {
Some(x) => println!("{}", x),
None => eprintln!("Almost three weeks from now overflows!"),
}
match now.checked_add_signed(Duration::max_value()) {
Some(x) => println!("{}", x),
None => eprintln!("We can't use chrono to tell the time for the Solar System to complete more than one full orbit around the galactic center."),
}
}
Convert a local time to another timezone
Gets the local time and displays it using offset::Local::now
and then converts it to the UTC standard using the DateTime::from_utc
struct method. A time is then converted using the offset::FixedOffset
struct and the UTC time is then converted to UTC+8 and UTC-2.
use chrono::{DateTime, FixedOffset, Local, Utc};
fn main() {
let local_time = Local::now();
let utc_time = DateTime::<Utc>::from_utc(local_time.naive_utc(), Utc);
let china_timezone = FixedOffset::east(8 * 3600);
let rio_timezone = FixedOffset::west(2 * 3600);
println!("Local time now is {}", local_time);
println!("UTC time now is {}", utc_time);
println!(
"Time in Hong Kong now is {}",
utc_time.with_timezone(&china_timezone)
);
println!("Time in Rio de Janeiro now is {}", utc_time.with_timezone(&rio_timezone));
}