diff --git a/src/cookbook/datetime/parsing.md b/src/cookbook/datetime/parsing.md index 7a3afa08..aee55576 100644 --- a/src/cookbook/datetime/parsing.md +++ b/src/cookbook/datetime/parsing.md @@ -1 +1,114 @@ # 解析和显示 + +### 检查日期和时间 +通过 [DateTime](https://docs.rs/chrono/*/chrono/struct.DateTime.html) 获取当前的 UTC 时间: +- [Timelike](https://docs.rs/chrono/*/chrono/trait.Timelike.html), 时/分/秒 +- [Datelike](https://docs.rs/chrono/*/chrono/trait.Datelike.html), 年/月/日 + +```rust,editable +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() + ); +} +``` + +### 日期和时间戳的相互转换 + +```rust,editable +use chrono::{NaiveDate, NaiveDateTime}; + +fn main() { + // 生成一个具体的日期时间 + 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 {}.", + // 打印日期和日期对应的时间戳 + date_time, date_time.timestamp()); + + // 计算从 1970 1月1日 0:00:00 UTC 开始,10亿秒后是什么日期时间 + 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); +} +``` + +### 显示格式化的日期和时间 +通过 [Utc::now](https://docs.rs/chrono/*/chrono/offset/struct.Utc.html#method.now) 可以获取当前的 UTC 时间。 + +```rust,editable +use chrono::{DateTime, Utc}; + +fn main() { + let now: DateTime = Utc::now(); + + println!("UTC now is: {}", now); + // 使用 RFC 2822 格式显示当前时间 + println!("UTC now in RFC 2822 is: {}", now.to_rfc2822()); + // 使用 RFC 3339 格式显示当前时间 + println!("UTC now in RFC 3339 is: {}", now.to_rfc3339()); + // 使用自定义格式显示当前时间 + println!("UTC now in a custom format is: {}", now.format("%a %b %e %T %Y")); +} +``` + +### 将字符串解析为 DateTime 结构体 +我们可以将多种格式的日期时间字符串转换成 [DateTime](https://docs.rs/chrono/*/chrono/struct.DateTime.html) 结构体。[DateTime::parse_from_str](https://docs.rs/chrono/*/chrono/struct.DateTime.html#method.parse_from_str) 使用的转义序列可以在 [chrono::format::strftime](https://docs.rs/chrono/0.4.19/chrono/format/strftime/index.html) 找到. + +只有当能唯一的标识出日期和时间时,才能创建 `DateTime`。如果要在没有时区的情况下解析日期或时间,你需要使用 [`NativeDate`](https://docs.rs/chrono/*/chrono/naive/struct.NaiveDate.html) 等函数。 + +```rust,editable +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(()) +} +``` \ No newline at end of file