Turn a time into a time-zoned future timestamp (date-fns + date-fns-timezone)

timestampJawn.js

const { 
  convertToTimeZone 
} = require('date-fns-timezone');
const dateFns = require("date-fns");
const { 
  format,
  getTime, 
  startOfToday,
  parse,
  addDays,
} = dateFns;

// given a human legible string time + timezone, 
// return the next available time in that timezone.
// no past timestamps allowed.
const getTzTimestamp = (
  time = '4:20 PM', 
  timeZone = 'America/New_York'
) => {
  let now= convertToTimeZone(
    new Date(), 
    { timeZone }
  );
  let nowStamp= getTime(now);
  let day = parse(
    time, 
    'h:mm a', 
    now
  );
  let tzStamp= getTime(day);
  if(now > day){
    day= addDays(day, 1);
  };
  let timestamp = getTime(day);
  let string= format(day, 'LLL do @ h:mm a')
  return { day, timestamp, string };
};

const t= '11:48 PM';
//const nd= getTzTimestamp(t, 'America/North_Dakota/Center');
const la= getTzTimestamp(t, 'America/Los_Angeles');
const ny= getTzTimestamp(t, 'America/New_York');
console.log({t});
console.table({ ny, la });
/*

{ t: '11:48 PM' }
┌─────────┬──────────────────────────┬───────────────┬──────────────────────┐
│ (index) │           day            │   timestamp   │        string        │
├─────────┼──────────────────────────┼───────────────┼──────────────────────┤
│   ny    │ 2020-10-02T23:48:00.000Z │ 1601682480000 │ 'Oct 2nd @ 11:48 PM' │
│   la    │ 2020-10-02T23:48:00.000Z │ 1601682480000 │ 'Oct 2nd @ 11:48 PM' │
└─────────┴──────────────────────────┴───────────────┴──────────────────────┘

*/