为什么 Date.parse 给出不正确的结果? [英] Why does Date.parse give incorrect results?

问题描述

new Date(Date.parse("Jul 8, 2005"));

输出:

2005 年 7 月 8 日星期五 00:00:00 GMT-0700(太平洋标准时间)

Output:

Fri Jul 08 2005 00:00:00 GMT-0700 (PST)

new Date(Date.parse("2005-07-08"));

输出:

2005 年 7 月 7 日星期四 17:00:00 GMT-0700(太平洋标准时间)

Output:

Thu Jul 07 2005 17:00:00 GMT-0700 (PST)

为什么第二次解析不正确?

Why is the second parse incorrect?

推荐答案

直到第 5 版规范出来，Date.parse 方法完全实现依赖(new Date(string) 等价于Date.parse(string) 除外后者返回一个数字而不是一个 Date).在第 5 版规范中添加了要求以支持 简化(稍微不正确) ISO-8601(另见 JavaScript 中的有效日期时间字符串是什么?).但除此之外，没有要求 Date.parse/new Date(string) 应该接受什么，除了他们必须接受任何 Date#toString 输出(不说那是什么).

Until the 5th edition spec came out, the Date.parse method was completely implementation dependent (new Date(string) is equivalent to Date.parse(string) except the latter returns a number rather than a Date). In the 5th edition spec the requirement was added to support a simplified (and slightly incorrect) ISO-8601 (also see What are valid Date Time Strings in JavaScript?). But other than that, there was no requirement for what Date.parse / new Date(string) should accept other than that they had to accept whatever Date#toString output (without saying what that was).

从 ECMAScript 2017(第 8 版)开始，实现需要解析 Date#toString 和 Date#toUTCString 的输出，但这些字符串的格式不是指定.

As of ECMAScript 2017 (edition 8), implementations were required to parse their output for Date#toString and Date#toUTCString, but the format of those strings was not specified.

从 ECMAScript 2019(第 9 版)开始，的格式Date#toString 和 Date#toUTCString，已被指定为(分别):

As of ECMAScript 2019 (edition 9) the format for Date#toString and Date#toUTCString, have been specified as (respectively):

1. ddd MMM DD YYYY HH:mm:ss ZZ [(时区名称)]
   例如2018 年 7 月 10 日星期二 18:39:58 GMT+0530 (IST)
2. ddd, DD MMM YYYY HH:mm:ss Z
   例如格林威治标准时间 2018 年 7 月 10 日，星期二 13:09:58

提供另外 2 种格式，Date.parse 应该在新的实现中可靠地解析这些格式(注意支持并不普遍，不合规的实现将继续使用一段时间).

providing 2 more formats that Date.parse should parse reliably in new implementations (noting that support is not ubiquitous and non–compliant implementations will remain in use for some time).

我建议手动解析日期字符串和 日期构造函数 与年、月和日参数一起使用以避免歧义:

I would recommend that date strings are parsed manually and the Date constructor used with year, month and day arguments to avoid ambiguity:

// parse a date in yyyy-mm-dd format
function parseDate(input) {

  let parts = input.split('-');

  // new Date(year, month [, day [, hours[, minutes[, seconds[, ms]]]]])
  return new Date(parts[0], parts[1]-1, parts[2]); // Note: months are 0-based
}

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