rust chrono

use chrono::prelude::*;

// 1. 时间转字符
// 2. 字符转时间
// 3. 时间相加减
// 4. 时间加差异数

fn main(){
    let d = NaiveDate::from_ymd(2015, 3, 14);
    let a = NaiveDate::from_ymd(2015, 3, 16);
    let a_b :i64 = (d-a).num_days();
    // println!("{:?}", (d-a).num_days());
    // let c = a + chrono::Duration::from(1);
    // println!("{:?}", c);

    let x = NaiveDate::parse_from_str("2015/9/30", "%Y/%m/%d");
    // println!("{:?}",x);

    let y = x.unwrap() + chrono::Duration::days(-1_i64);　　//i64类型
    print!(" => {:?}", y);
}