Rust: chrono庫，date,time及其它_rust

Parsing can be done with three methods:

The standard FromStr trait (and parse method on a string) can be used for parsing DateTime, DateTime and DateTime values. This parses what the {:?} (std::fmt::Debug) format specifier prints, and requires the offset to be present.

DateTime::parse_from_str parses a date and time with offsets and returns DateTime. This should be used when the offset is a part of input and the caller cannot guess that. It cannot be used when the offset can be missing. DateTime::parse_from_rfc2822 and DateTime::parse_from_rfc3339 are similar but for well-known formats.

Offset::datetime_from_str is similar but returns DateTime of given offset. When the explicit offset is missing from the input, it simply uses given offset. It issues an error when the input contains an explicit offset different from the current offset.

use chrono::prelude::*;let dt = UTC.ymd(2014, 11, 28).and_hms(12, 0, 9);let fixed_dt = dt.with_timezone(&FixedOffset::east(9*3600));// method 1assert_eq!("2014-11-28T12:00:09Z".parse::<DateTime<UTC>>(), Ok(dt.clone()));assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<UTC>>(), Ok(dt.clone()));assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<FixedOffset>>(), Ok(fixed_dt.clone()));// method 2assert_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00", "%Y-%m-%d %H:%M:%S %z"),           Ok(fixed_dt.clone()));assert_eq!(DateTime::parse_from_rfc2822("Fri, 28 Nov 2014 21:00:09 +0900"),           Ok(fixed_dt.clone()));assert_eq!(DateTime::parse_from_rfc3339("2014-11-28T21:00:09+09:00"), Ok(fixed_dt.clone()));// method 3assert_eq!(UTC.datetime_from_str("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone()));assert_eq!(UTC.datetime_from_str("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));// oops, the year is missing!assert!(UTC.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T %Y").is_err());// oops, the format string does not include the year at all!assert!(UTC.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T").is_err());// oops, the weekday is incorrect!assert!(UTC.datetime_from_str("Sat Nov 28 12:00:09 2014", "%a %b %e %T %Y").is_err());