Cookbooks
Rust
Chapter 7. Dates and Times
Calculating a date in the future or past

Rust:
Calculating a date in the future or past

How to:

Rust has the chrono crate for all your date and time needs. Here’s how to add to or subtract from a date:

use chrono::{DateTime, Duration, Utc};

fn main() {
    let now = Utc::now();
    println!("Current UTC time: {}", now);

    let two_weeks = Duration::weeks(2);
    let future_date = now + two_weeks;
    println!("UTC in two weeks: {}", future_date);

    let thirty_days_ago = Duration::days(-30);
    let past_date = now + thirty_days_ago;
    println!("UTC 30 days ago: {}", past_date);
}

Sample output:

Current UTC time: 2023-04-01T12:00:00Z
UTC in two weeks: 2023-04-15T12:00:00Z
UTC 30 days ago: 2023-03-02T12:00:00Z

Deep Dive

Traditionally, date and time manipulation has been a pain. Different systems and programming languages handle it in various ways. Rust’s standard library provides basic functionality, but the chrono crate is the go-to.

Alternatives? Sure, you could manually calculate dates by converting everything to timestamps, manipulating the numbers, and converting back. Or, you could use time-specific libraries in other languages—Python has datetime, JavaScript has Date, and so on.

The chrono crate in Rust gives you time-zone aware types like DateTime, and durations as seen above. It handles all the messy bits like leap years and daylight savings so you don’t have to. It also does date parsing and formatting, making it a comprehensive solution.

See Also

Comparing two dates