Type Alias instant::SystemTime

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pub type SystemTime = SystemTime;

Aliased Type§

struct SystemTime(/* private fields */);

Implementations

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impl SystemTime

1.28.0 · source

pub const UNIX_EPOCH: SystemTime = UNIX_EPOCH

An anchor in time which can be used to create new SystemTime instances or learn about where in time a SystemTime lies.

This constant is defined to be “1970-01-01 00:00:00 UTC” on all systems with respect to the system clock. Using duration_since on an existing SystemTime instance can tell how far away from this point in time a measurement lies, and using UNIX_EPOCH + duration can be used to create a SystemTime instance to represent another fixed point in time.

duration_since(UNIX_EPOCH).unwrap().as_secs() returns the number of non-leap seconds since the start of 1970 UTC. This is a POSIX time_t (as a u64), and is the same time representation as used in many Internet protocols.

Examples

use std::time::SystemTime;

match SystemTime::now().duration_since(SystemTime::UNIX_EPOCH) {
    Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
    Err(_) => panic!("SystemTime before UNIX EPOCH!"),
}

1.8.0 · source

pub fn now() -> SystemTime

Returns the system time corresponding to “now”.

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();

1.8.0 · source

pub fn duration_since( &self, earlier: SystemTime ) -> Result<Duration, SystemTimeError>

Returns the amount of time elapsed from an earlier point in time.

This function may fail because measurements taken earlier are not guaranteed to always be before later measurements (due to anomalies such as the system clock being adjusted either forwards or backwards). Instant can be used to measure elapsed time without this risk of failure.

If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from the specified measurement to this one.

Returns an Err if earlier is later than self, and the error contains how far from self the time is.

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();
let new_sys_time = SystemTime::now();
let difference = new_sys_time.duration_since(sys_time)
    .expect("Clock may have gone backwards");
println!("{difference:?}");

1.8.0 · source

pub fn elapsed(&self) -> Result<Duration, SystemTimeError>

Returns the difference from this system time to the current clock time.

This function may fail as the underlying system clock is susceptible to drift and updates (e.g., the system clock could go backwards), so this function might not always succeed. If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from this time measurement to the current time.

To measure elapsed time reliably, use Instant instead.

Returns an Err if self is later than the current system time, and the error contains how far from the current system time self is.

Examples

use std::thread::sleep;
use std::time::{Duration, SystemTime};

let sys_time = SystemTime::now();
let one_sec = Duration::from_secs(1);
sleep(one_sec);
assert!(sys_time.elapsed().unwrap() >= one_sec);

1.34.0 · source

pub fn checked_add(&self, duration: Duration) -> Option<SystemTime>

Returns Some(t) where t is the time self + duration if t can be represented as SystemTime (which means it’s inside the bounds of the underlying data structure), None otherwise.

1.34.0 · source

pub fn checked_sub(&self, duration: Duration) -> Option<SystemTime>

Returns Some(t) where t is the time self - duration if t can be represented as SystemTime (which means it’s inside the bounds of the underlying data structure), None otherwise.

Trait Implementations

1.8.0 · source§

impl Add<Duration> for SystemTime

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fn add(self, dur: Duration) -> SystemTime

Panics

This function may panic if the resulting point in time cannot be represented by the underlying data structure. See SystemTime::checked_add for a version without panic.

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