如何在 Javascript 中将带有 3 个字母时区缩写的日期转换为 UTC？

Question

I need to convert datetimes from an input format which I can't change (this: "Tue, 30 Jul 2019 21:15:53 GMT") to UTC, in Javascript.

I actually need to get these dates as the number of milliseconds since the Unix epoch (1970) but getting in UTC would be a start.

Is there a way to do this easily? I can use a 3rd party library if needed. I've heard of moment-timezone.js but not clear how to parse the 3 letter timezone, ie these: https://en.wikipedia.org/wiki/List_of_time_zone_abbreviations .

Answer 1

The correct solution is a library that maps these abbreviations to offsets from GMT. Neither moment-timezone , nor date-fns-tz , nor luxon , nor timezone-support do this, but timezone-abbr-offsets does and is very minimalistic .

Fortunately, new Date() can parse your format minus the timezone, so we'll split that away and calculate the offset back:

import timezones from 'timezone-abbr-offsets';

function abbrTzToUtc(dateString) {
  // Get the date and the timezone from the input string
  let [, date, tz] = dateString.match(/^(.*)\s+(\w+)$/);
  // Ignore the timezone and parse the date as GMT
  date = new Date(date + 'Z');
  // Add the offset caused by the original timezone
  date = new Date(date.getTime() + timezones[tz] * 60 * 1000);
  return date;
}

console.log(abbrTzToUtc('Tue, 30 Jul 2019 21:15:53 MET'));

As a test, the code above should return 2019-07-30T22:15:53.000Z .

If you want number of milliseconds since the Unix epoch, return date.getTime() instead.

Answer 2

If you want to convert the date into UTC format you can use toISOString()

new Date('Tue, 30 Jul 2019 21:15:53 GMT').toISOString()

For more info please check this reference

Moreover, to convert the date into milliseconds you can use Date.UTC()

Date.UTC(year[, month[, day[, hour[, minute[, second[, millisecond]]]]]])

reference

Example:

utcMillisecond = (e) => {
    const regex = /(T)|(:)|(-)/g;
    const utc = new Date(e).toISOString().slice(0, 19).replace(regex, ' ').split(' ');
    const utcMillisecond = Date.UTC(utc[0], utc[1], utc[2], utc[3], utc[4])
    return utcMillisecond
}

utcMillisecond("Tue, 30 Jul 2019 21:15:53 GMT")
//1567199700000