DateTime获取当前的 UTC，还有Timelike，能得到它的小时/分钟/秒（hour/minute/second），通过Datelike，则能获得它的年/月/日/周末（year/month/day/weekday）。

extern crate chrono;
use chrono::{Datelike, Timelike, Utc};

fn main() {
    let now = Utc::now();

    let (is_pm, hour) = now.hour12();
    println!(
        "The current UTC time is {:02}:{:02}:{:02} {}",
        hour,
        now.minute(),
        now.second(),
        if is_pm { "PM" } else { "AM" }
    );
    println!(
        "And there have been {} seconds since midnight",
        now.num_seconds_from_midnight()
    );

    let (is_common_era, year) = now.year_ce();
    println!(
        "The current UTC date is {}-{:02}-{:02} {:?} ({})",
        year,
        now.month(),
        now.day(),
        now.weekday(),
        if is_common_era { "CE" } else { "BCE" }
    );
    println!(
        "And the Common Era began {} days ago",
        now.num_days_from_ce()
    );
}

NaiveDate::from_ymd和NaiveTime::from_hms给出一个日期，用NaiveDateTime::timestamp转换到UNIX 时间戳。然后使用NaiveDateTime::from_timestamp，它计算从 1970 1，01 0:00:00 UTC 开始，10 亿秒后的日期。

extern crate chrono;

use chrono::{NaiveDate, NaiveDateTime};

fn main() {
    let date_time: NaiveDateTime = NaiveDate::from_ymd(2017, 11, 12).and_hms(17, 33, 44);
    println!(
        "Number of seconds between 1970-01-01 00:00:00 and {} is {}.",
        date_time, date_time.timestamp());

    let date_time_after_a_billion_seconds = NaiveDateTime::from_timestamp(1_000_000_000, 0);
    println!(
        "Date after a billion seconds since 1970-01-01 00:00:00 was {}.",
        date_time_after_a_billion_seconds);
}

使用Utc::now，获取并显示当前时间（以 UTC 为单位）。以众所周知的格式RFC 2822，格式化当前时间，通过DateTime::to_rfc2822。还有RFC 3339格式，可以使用DateTime::to_rfc3339，除此之外，用DateTime::format可以自定义格式。

extern crate chrono;
use chrono::{DateTime, Utc};

fn main() {
    let now: DateTime<Utc> = Utc::now();

    println!("UTC now is: {}", now);
    println!("UTC now in RFC 2822 is: {}", now.to_rfc2822());
    println!("UTC now in RFC 3339 is: {}", now.to_rfc3339());
    println!("UTC now in a custom format is: {}", now.format("%a %b %e %T %Y"));
}

解析已知的字符串表达格式RFC 2822，RFC 3339和自定义格式，将其变为一个DateTime结构，可以分别使用DateTime::parse_from_rfc2822，DateTime::parse_from_rfc3339和DateTime::parse_from_str。

可以在chrono::format::strftime找到，转义序列，让其可用于DateTime::format。 请注意DateTime::parse_from_str要求一个 DateTime 结构，必须是创建的，唯一标识的日期和时间。请使用NaiveDate，NaiveTime和NaiveDateTime，分析没有时区的日期和时间。

extern crate chrono;
use chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime};
use chrono::format::ParseError;


fn main() -> Result<(), ParseError> {
    let rfc2822 = DateTime::parse_from_rfc2822("Tue, 1 Jul 2003 10:52:37 +0200")?;
    println!("{}", rfc2822);

    let rfc3339 = DateTime::parse_from_rfc3339("1996-12-19T16:39:57-08:00")?;
    println!("{}", rfc3339);

    let custom = DateTime::parse_from_str("5.8.1994 8:00 am +0000", "%d.%m.%Y %H:%M %P %z")?;
    println!("{}", custom);

    let time_only = NaiveTime::parse_from_str("23:56:04", "%H:%M:%S")?;
    println!("{}", time_only);

    let date_only = NaiveDate::parse_from_str("2015-09-05", "%Y-%m-%d")?;
    println!("{}", date_only);

    let no_timezone = NaiveDateTime::parse_from_str("2015-09-05 23:56:04", "%Y-%m-%d %H:%M:%S")?;
    println!("{}", no_timezone);

    Ok(())
}