Function isoStringToDate

packages/common/src/i18n/format_date.ts:973–997

(match: RegExpMatchArray)

 * Used instead of `Date.parse` because of browser discrepancies.
 */
export function isoStringToDate(match: RegExpMatchArray): Date {
  const date = new Date(0);
  let tzHour = 0;
  let tzMin = 0;

  // match[8] means that the string contains "Z" (UTC) or a timezone like "+01:00" or "+0100"
  const dateSetter = match[8] ? date.setUTCFullYear : date.setFullYear;
  const timeSetter = match[8] ? date.setUTCHours : date.setHours;

  // if there is a timezone defined like "+01:00" or "+0100"
  if (match[9]) {
    tzHour = Number(match[9] + match[10]);
    tzMin = Number(match[9] + match[11]);
  }
  dateSetter.call(date, Number(match[1]), Number(match[2]) - 1, Number(match[3]));
  const h = Number(match[4] || 0) - tzHour;
  const m = Number(match[5] || 0) - tzMin;
  const s = Number(match[6] || 0);
  // The ECMAScript specification (https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.11)
  // defines that `DateTime` milliseconds should always be rounded down, so that `999.9ms`
  // becomes `999ms`.
  const ms = Math.floor(parseFloat('0.' + (match[7] || 0)) * 1000);
  timeSetter.call(date, h, m, s, ms);
  return date;
}

export function isDate(value: any): value is Date {
  return value instanceof Date && !isNaN(value.valueOf());