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chrono.md

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Sure! Here’s a summary of commonly used functions and types from the Rust chrono crate, with simple examples to demonstrate how to use them.

Chrono Crate — Key Functions & Examples

1. Import basics

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

2. Getting current time

let now_utc: DateTime<Utc> = Utc::now();
println!("Current UTC time: {}", now_utc);

let now_local: DateTime<Local> = Local::now();
println!("Current Local time: {}", now_local);

3. Creating dates and times

  • NaiveDate (date without timezone)
let date = NaiveDate::from_ymd(2025, 7, 28);
println!("NaiveDate: {}", date);
  • NaiveTime (time without date or timezone)
let time = NaiveTime::from_hms(14, 30, 0);
println!("NaiveTime: {}", time);
  • NaiveDateTime (date + time without timezone)
let datetime = NaiveDateTime::new(date, time);
println!("NaiveDateTime: {}", datetime);

4. Parsing from strings

// Parsing RFC3339 datetime string with timezone
let dt = DateTime::parse_from_rfc3339("2025-07-28T14:30:00+02:00").unwrap();
println!("Parsed DateTime: {}", dt);

// Parsing naive date from string with format
let nd = NaiveDate::parse_from_str("2025-07-28", "%Y-%m-%d").unwrap();
println!("Parsed NaiveDate: {}", nd);

5. Formatting dates/times

let now = Utc::now();

// Format as YYYY-MM-DD HH:MM:SS
println!("Formatted date: {}", now.format("%Y-%m-%d %H:%M:%S"));

// Format with weekday name
println!("Formatted with weekday: {}", now.format("%A, %B %d, %Y"));

6. Adding and subtracting durations

let now = Utc::now();
let later = now + Duration::days(5);
let earlier = now - Duration::hours(3);

println!("5 days later: {}", later);
println!("3 hours earlier: {}", earlier);

7. Working with durations

let dur = Duration::seconds(3600);  // 1 hour
println!("Duration in seconds: {}", dur.num_seconds());
println!("Duration in minutes: {}", dur.num_minutes());

8. Timezone conversions

let utc_time = Utc::now();
let local_time = utc_time.with_timezone(&Local);
println!("UTC time: {}", utc_time);
println!("Local time: {}", local_time);

9. Extracting date/time components

let now = Utc::now();

println!("Year: {}", now.year());
println!("Month: {}", now.month());
println!("Day: {}", now.day());
println!("Hour: {}", now.hour());
println!("Minute: {}", now.minute());
println!("Second: {}", now.second());

10. Creating Date from NaiveDate and timezone

let naive_date = NaiveDate::from_ymd(2025, 7, 28);
let date = Utc.from_utc_date(&naive_date);
println!("Date with timezone: {}", date);

11. Getting timestamp and converting from timestamp

let now = Utc::now();
let timestamp = now.timestamp();
println!("Unix timestamp: {}", timestamp);

let dt_from_ts = Utc.timestamp(timestamp, 0);
println!("DateTime from timestamp: {}", dt_from_ts);

12. Comparing dates/times

let dt1 = Utc::now();
let dt2 = dt1 + Duration::days(1);

println!("dt1 < dt2? {}", dt1 < dt2);
println!("dt1 == dt2? {}", dt1 == dt2);

13. Extracting weekday

let now = Utc::now();
println!("Weekday: {}", now.weekday());  // e.g., "Mon"

Summary Table of Common Types and Their Methods

Type Purpose Example Method
DateTime<Tz> Date & time with timezone now(), format(), timestamp(), with_timezone()
NaiveDate Date without timezone from_ymd(), parse_from_str(), year(), month()
NaiveTime Time without timezone from_hms(), hour(), minute()
NaiveDateTime Date & time without timezone new(), parse_from_str()
Duration Time duration (interval) days(), seconds(), num_minutes()
TimeZone Trait for timezone conversions from_utc_date(), timestamp()