translating a provided date to a given timezone with moment-timezone

index.js

var moment = require('moment-timezone')

console.log(midnightPst('2017-12-31T13:59:59.999Z')) // provided as 11:59 HAST
console.log(midnightPst('2018-01-01T07:59:59.999Z')) // provided as 11:59 PST
console.log(midnightPst('2018-01-01T04:59:59.999Z')) // provided as 11:59 EST
console.log(midnightPst('2018-12-31T23:59:59.999Z')) // provided as 11:59 UTC

// east of GMT doesn't work.
console.log(midnightPst('2018-01-01T08:59:59.999Z')) // provided as 11:59 JST

function midnightPst (date) {

	var dateUtc = moment(date)
	
	// use moment.tz to translate this to PST
	// from here, pull out the yyyy-mm-dd
	// these will now be in PST, so instead of 8am jan.1 it is 12pm dec.31
	// this breaks if the translation is AFTER gmt, it'll be a day out :(
	
	var datePst = moment.tz(dateUtc, 'Canada/Pacific')
	var year = datePst.year()    // 2017
	var month = datePst.month()  // 12
	var date = datePst.date()    // 31
	
	// generate moment array constructor - this bypasses current tz of system (utc)
	// and will create a date timestamp for the provided format
	
	return moment.tz([year, month, date], 'Canada/Pacific')
		.endOf('day')
		.format('YYYY-MM-DDTHH:mm:ss.SSSSZ')
}

// TZ=UTC node index.js
// 2017-12-31T23:59:59.9990-08:00
// 2017-12-31T23:59:59.9990-08:00
// 2017-12-31T23:59:59.9990-08:00
// 2018-12-31T23:59:59.9990-08:00
// 2018-01-01T23:59:59.9990-08:00  aww, so close.
//
// I hate dates.