How to use chrono crate in Rust date and time

Crates/Chrono
2026-04-17T16:46:41+00:00
The `chrono` crate provides the `NaiveDateTime` and `DateTime` types for handling dates and times, with `DateTime<Tz>` being the standard choice for timezone-aware operations.

The chrono crate provides the NaiveDateTime and DateTime types for handling dates and times, with DateTime<Tz> being the standard choice for timezone-aware operations. You typically create instances using the from_str method for parsing or the now() method for the current time, then format or manipulate them using the format method and arithmetic operators.

First, add the crate to your Cargo.toml:

[dependencies]
chrono = "0.4"

Here is a practical example showing how to parse a string, get the current time, and perform basic formatting and arithmetic:

use chrono::{DateTime, NaiveDateTime, Utc, Local, TimeZone};

fn main() {
    // 1. Parse a date string (ISO 8601 format)
    let parsed: NaiveDateTime = "2023-10-27 14:30:00".parse().unwrap();
    println!("Parsed naive: {}", parsed);

    // 2. Get current time in UTC and Local timezone
    let now_utc: DateTime<Utc> = Utc::now();
    let now_local: DateTime<Local> = Local::now();

    println!("UTC: {}", now_utc.format("%Y-%m-%d %H:%M:%S"));
    println!("Local: {}", now_local.format("%Y-%m-%d %H:%M:%S"));

    // 3. Convert between timezones
    let utc_to_local = now_utc.with_timezone(&Local);
    println!("Converted to local: {}", utc_to_local);

    // 4. Arithmetic: Add 24 hours to a DateTime
    let tomorrow = now_utc + chrono::Duration::hours(24);
    println!("Tomorrow: {}", tomorrow);

    // 5. Custom formatting
    let formatted = now_utc.format("%A, %B %d, %Y at %I:%M %p").to_string();
    println!("Formatted: {}", formatted);
}

Key patterns to remember:

  • Use NaiveDateTime when you don't care about timezones (e.g., storing a date in a database without context).
  • Use DateTime<Tz> (where Tz is Utc, Local, or a specific FixedOffset) for any operation involving real-world time or timezone conversion.
  • Parsing requires the input string to match the expected format; use parse() for ISO 8601 or DateTime::parse_from_str() with a custom format string for others.
  • Formatting uses the same syntax as C's strftime (e.g., %Y for year, %m for month).
  • Arithmetic is done via Duration from the std::time module or chrono::Duration for more precise control.

Avoid mixing NaiveDateTime and DateTime directly; always convert to a timezone-aware type before performing operations that depend on local time or daylight saving rules.