Wrong timezone used for implicit year/month/day

[murrayju]

This is probably only an issue around new year's day. If I parse a date like the following:

moment.tz('December 31 5:00PM', 'MMMM D h:mmA', 'America/Denver')

My expectation is that it will implicitly use the current year in the America/Denver timezone (which is currently 2019). Instead, it seems to be assuming the year that it is in GMT, resulting in the date being parsed as 2021-01-01T00:00:00.000Z which is a year in the future, instead of today.

[murrayju]

Month and day have the same problem. I'm intending to use this to parse times (e.g. 5:00PM) that implicitly have "today's" date in the given time zone.

Fortunately,

moment.tz('America/Denver').format('YYYY-MM-DD')

gives the correct/expected result (2019-12-31), so I'm able to use this as a dirty workaround:

moment.tz(
  `${moment.tz('America/Denver').format('YYYY-MM-DD')} 5:00PM`,
  'YYYY-MM-DD h:mmA',
  'America/Denver',
)

[ellenaua]

@murrayju how did you get 2021-01-01T00:00:00.000Z? Did you use .toISOString() method?

See my results:

const moment = require('moment-timezone');
const date = moment.tz('December 31 5:00PM', 'MMMM D h:mmA', 'America/Denver')

console.log(date.toISOString()); // 2021-01-01T00:00:00.000Z -- correct, 00:00 UTC
console.log(date.format()); // 2020-12-31T17:00:00-07:00 -- correct, 17:00 in Denver
console.log(date.toString());  // Thu Dec 31 2020 17:00:00 GMT-0700 - correct, 17:00 in Denver

[ellenaua]

or you used methods like '.getDate()', '.getFullYear()', '.getDate()' which resulted to this:

const date = moment.tz('December 31 5:00PM', 'MMMM D h:mmA', 'America/Denver').toDate()
console.log(date.getFullYear()) // 2021
console.log(date.getMonth()) // 0
console.log(date.getDate()) // 1

You should use .format() to get correct values:

const date = moment.tz('December 31 5:00PM', 'MMMM D h:mmA', 'America/Denver');
console.log(date.format('YYYY')) // 2020
console.log(date.format('M')) // 12
console.log(date.format('D')) // 31

[murrayju]

I used toISOString(). The point is that I got the value that you currently say is correct, when the local time was last year (2019). The point of the code is to interpret a given time with today's date in a given time zone. It usually works, but there is a window of time on new year's eve that incorrectly gives a date one year in the future instead.

This is a bug report, not a question.

[ellenaua]

I finally succeeded to reproduce it, thanks for reporting. This is how it can be reproduced:

const sinon = require('sinon');

sinon.useFakeTimers(new Date('2019-12-31T19:00:00-07:00'));

const date1 = moment.tz('December 31 9:00PM', 'MMMM D h:mmA', 'America/Denver');
const date2 = moment.tz('2019 December 31 9:00PM', 'YYYY MMMM D h:mmA', 'America/Denver');

console.log(date1.toISOString()); // 2021-01-01T04:00:00.000Z
console.log(date2.toISOString()); // 2020-01-01T04:00:00.000Z

[ichernev]

This is a duplicate of #874, closing this for now.