javascript - Moment js time zone date conversion issue

Question

I am using moment js to convert user system time to user specified time zone as per his preference. User system time zone is IST and he is specifing a different time zone. For setting the same I am using

moment.tz.setDefault("Pacific/Pago_Pago");

But in one of the scenario I am getting different dates. If I do

moment().startOf('day')

I am getting today's date as Thu Oct 28 2021 00:00:00 GMT+0530 (India Standard Time), But if I am doing

moment(endDate).startOf('day')

I am getting Thu Oct 27 2021 00:00:00 GMT+0530 (India Standard Time) Where end date is the result of last statement i.e. Thu Oct 28 2021 00:00:00 GMT+0530 (India Standard Time)

What I am doing wrong here.

标签： javascriptdatetimetimezonemomentjsmoment-timezone

Answer 1

创建时刻对象时使用的时区保留为对象的一部分，并用于后续处理。如果在创建初始时刻对象后更改默认时区，则会发生所描述的效果。

例如

// Set default to IST (+5:30)
moment.tz.setDefault('Asia/Kolkata');

// Create initial moment using default timezone
let start = moment().startOf('day');

// Changing the default here doesn't affect above moment
moment.tz.setDefault('Pacific/Pago_Pago');

// This still uses the initial +5:30 offset, not -11:00 for Pago Pago
let timestamp = start.toString();

// This uses the timestamp for the original timezone, but
// then gets start of day in new default timezone
let end = moment(timestamp).startOf('day');

console.log( `Start: ${start.toString()}\nEnd  : ${end.toString()}` );

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.9.0/moment-with-locales.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.31/moment-timezone-with-data-10-year-range.js"></script>