Check if a date string is in ISO and UTC format

Try this – you need to actually create a date object rather than parsing the string

NOTE: This will test the string AS YOU POSTED IT.

YYYY-MM-DDTHH:MN:SS.MSSZ

It will fail on valid ISO8601 dates like

• Date: 2018-10-18
• Combined date and time in UTC: 2018-10-18T08:04:30+00:00 (without the Z and TZ in 00:00)
• 2018-10-18T08:04:30Z
• 20181018T080430Z
• Week: 2018-W42
• Date with week number: 2018-W42-4
• Date without year: –10-18 (last in ISO8601:2000, in use by RFC 6350[2])
• Ordinal date: 2018-291

It will no longer accept INVALID date strings

function isIsoDate(str) {
  if (!/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}Z/.test(str)) return false;
  const d = new Date(str); 
  return d instanceof Date && !isNaN(d.getTime()) && d.toISOString()===str; // valid date 
}

console.log(isIsoDate('2011-10-05T14:48:00.000Z'))

console.log(isIsoDate('2018-11-10T11:22:33+00:00'));

console.log(isIsoDate('2011-10-05T14:99:00.000Z')); // invalid time part