shift-timezone-offset

shift-timezone-offset

Converts timezoned dates to local time or any other timezone.

Sometimes it's easier to work in local time, because all JavaScript Date objects are given in local time:

new Date('2017-01-01T00:00:00Z').getHours()

// => 11 

It's because my timezone is +11:00, fine, but I would like a 0!

This library will shift a date to match time in the local timezone, or the one you need, as if the timezone information is ignored.

example

Working in local time:

// process.env.TZ = 'Pacific/Noumea' // local timezone

var timezoneShift = require('../')
var dateInfo = '2017-01-01T00:00:00+03:00'
var initialDate = new Date(dateInfo)

console.log(initialDate.getHours())
// => 8

console.log(initialDate.getTime() / 1000)
// => 1483218000

var converter = timezoneShift('+03:00') // timezoneShift(dateInfo) works as well
var localDate = converter.toLocal(initialDate)

console.log(localDate.getHours())
// => 0

console.log(localDate.getTime() / 1000)
// => 1483189200

var backToInitialDate = converter.fromLocal(localDate)

console.log(backToInitialDate.getHours())
// => 8

console.log(backToInitialDate.getTime() / 1000)
// => 1483218000

When only one operation is needed, there is a shortcut notation:

var timezoneShift = require('../')
var dateInfo = '2017-01-01T12:00:00+03:00'

console.log(new Date(dateInfo))
// => 2017-01-01T09:00:00.000Z

// 5 hours timezone shift
console.log(timezoneShift.convert(dateInfo, { from: '+03:00', to: '+08:00' }))
// => 2017-01-01T04:00:00.000Z

// to local (all 3 are similar)
// "to" defaults to local timezone:
console.log(timezoneShift.convert(dateInfo, { from: '+03:00' }))
// => 2017-01-01T01:00:00.000Z

// to be sure:
console.log(timezoneShift.convert(dateInfo, { from: '+03:00', to: '+11:00' }))
// => 2017-01-01T01:00:00.000Z

// even simpler ("from" timezone is infered from date string):
console.log(timezoneShift.convert(dateInfo)) 
// => 2017-01-01T01:00:00.000Z

api

var timezoneShift = require('timezone-offset')

var converter = timezoneShift(validTimezone)

• validTimezone - valid ISO 8601 date string or timezone string: '+05:00', '-1100' or '2017-01-01T12:00:00+05:00'. An offset is valid as well: -240 in place of '+04:00.

converter.toLocal(date)

Shift a date considered in the converter timezone to the local timezone. It means the absolute UTC value is affected. Returns a new Date object.

• date - any valid value for the Date constructor.

converter.fromLocal(date)

Shift a local date to the timezone. It means the UTC value is affected. Returns a new Date object.

• date - any valid value for the Date constructor.

converter.toTimezone(date, zone)

Shift a local date to converter timezone. Returns a new Date object.

• date - any valid value for the Date constructor.
• zone - valid ISO 8601 date string or timezone string.

converter.offset

Timezone offset from UTC in minutes (similar to Date.prototype.getTimezoneOffset).

converter.timeShift

The full shift in minutes required to convert the dates to the local timezone.

timezoneShift.convert(date, zones)

• date - any valid value for the Date object constructor.
• zone - object containing initial and final timezones:
  • zones.from - valid timezone info. Could be infered if date is an ISO date string.
  • zones.to - default: local timezone. Valid timezone info.

license

MIT

install

npm install shift-timezone-offset