Moment.js - 在同一小时内添加分钟到最后一分钟的结果

Question

I'm currently trying to use moment.js (2.24.0) to add a minute to the last minute of a hour. However, it results in going back to the first minute of the same hour.

Here's an example code:

  var minute = '2019-11-03 01:59:00';
  console.log('Before: '+minute);
  minute = moment(minute, 'YYYY-MM-DD HH:mm:ss')
    .add(1, 'minutes')
    .format('YYYY-MM-DD HH:mm:00');
  console.log('After: '+minute);

This results in:

Before: 2019-11-03 01:59:00
After: 2019-11-03 01:00:00

Is this a bug or expected behavior for moment.js? If it's expected behavior, then how do I properly address it to go to the next hour.

Answer 1

In the US, daylight savings time ends at 2AM on 2019-11-03.

The behaviour you're seeing when adding a minute to 1:59AM isn't a bug but rather what will actually happen at that time. The calculation is based on your current timezone so 2019-11-03 01:59:00 EDT (Eastern Daylight Time) + 1 minute = 2019-11-03 01:00:00 EST (Eastern Standard Time).

If you were to run the same test at 2:59 instead of 1:59, it would increment as expected. You could specify that you actually mean 1:59AM EST but be sure that is in fact the case before attempting it.

Additional reading: https://momentjs.com/timezone/docs/#/using-timezones/parsing-ambiguous-inputs/