date-fns-tz/esm/_lib/tzParseTimezone/index.js

Time zone support for date-fns v2 with the browser Intl API

import tzTokenizeDate from '../tzTokenizeDate/index.js'

var MILLISECONDS_IN_HOUR = 3600000
var MILLISECONDS_IN_MINUTE = 60000

var patterns = {
  timezone: /([Z+-].*)$/,
  timezoneZ: /^(Z)$/,
  timezoneHH: /^([+-])(\d{2})$/,
  timezoneHHMM: /^([+-])(\d{2}):?(\d{2})$/,
  timezoneIANA: /(UTC|(?:[a-zA-Z]+\/[a-zA-Z_]+(?:\/[a-zA-Z_]+)?))$/,
}

// Parse various time zone offset formats to an offset in milliseconds
export default function tzParseTimezone(timezoneString, date) {
  var token
  var absoluteOffset

  // Z
  token = patterns.timezoneZ.exec(timezoneString)
  if (token) {
    return 0
  }

  var hours

  // ±hh
  token = patterns.timezoneHH.exec(timezoneString)
  if (token) {
    hours = parseInt(token[2], 10)

    if (!validateTimezone(hours)) {
      return NaN
    }

    absoluteOffset = hours * MILLISECONDS_IN_HOUR
    return token[1] === '+' ? -absoluteOffset : absoluteOffset
  }

  // ±hh:mm or ±hhmm
  token = patterns.timezoneHHMM.exec(timezoneString)
  if (token) {
    hours = parseInt(token[2], 10)
    var minutes = parseInt(token[3], 10)

    if (!validateTimezone(hours, minutes)) {
      return NaN
    }

    absoluteOffset = hours * MILLISECONDS_IN_HOUR + minutes * MILLISECONDS_IN_MINUTE
    return token[1] === '+' ? -absoluteOffset : absoluteOffset
  }

  // IANA time zone
  token = patterns.timezoneIANA.exec(timezoneString)
  if (token) {
    date = new Date(date || Date.now())
    date.setMilliseconds(0)
    // var [fYear, fMonth, fDay, fHour, fMinute, fSecond] = tzTokenizeDate(date, timezoneString)
    var tokens = tzTokenizeDate(date, timezoneString)
    var asUTC = Date.UTC(tokens[0], tokens[1] - 1, tokens[2], tokens[3], tokens[4], tokens[5])
    return -(asUTC - date.getTime())
  }

  return 0
}

function validateTimezone(hours, minutes) {
  if (minutes != null && (minutes < 0 || minutes > 59)) {
    return false
  }

  return true
}