如何计算两个 chrono::DateTime 之间的持续时间？

Question

我正在使用chrono crate，想要计算Duration两个DateTimes 之间的值。

use chrono::Utc;
use chrono::offset::TimeZone;

let start_of_period = Utc.ymd(2020, 1, 1).and_hms(0, 0, 0);
let end_of_period = Utc.ymd(2021, 1, 1).and_hms(0, 0, 0);

// What should I enter here?
//
// The goal is to find a duration so that
// start_of_period + duration == end_of_period
// I expect duration to be of type std::time
let duration = ... 

let nb_of_days = duration.num_days();

Answer 1

DateTime实现Sub<DateTime>，因此您只需从第一个日期中减去最近的日期即可：

let duration = end_of_period - start_of_period;
println!("num days = {}", duration.num_days());