Echo JS 0.11.0

Looks like I can do what I need with tz-offset, which is only ~18k unpacked compared to close to moment/moment-timezone which are MASSIVE.

    var tzOffset = require("tz-offset")

    function todayAtTime(input /*17:00*/) {
      const now = new Date();
      const y = now.getFullYear();
      const m = `0${now.getMonth() + 1}`.substr(-2);
      const d = `0${now.getDate()}`.substr(-2);
      
      const ret = `${y}-${m}-${d}T${input}`;
      return ret;
    }

    function inDst(dtm) {
        const dstStart = new Date(dtm.getFullYear(), 2/*Mar*/, 14, 2);
        const dstEnd = new Date(dtm.getFullYear(), 10/*Nov*/, 7, 3);
        return (dtm < dstStart || dtm > dstEnd);
    }

    function parseAsTimezone(input, timezone, noDst) {
        const dtm = new Date(input);
        dtm.setMinutes(
            dtm.getMinutes() 
            + (-1 * dtm.getTimezoneOffset())
            + tzOffset.offsetOf(timezone)
        );
        
        const dstStart = new Date(dtm.getFullYear(), 2/*Mar*/, 14, 2);
        const dstEnd = new Date(dtm.getFullYear(), 10/*Nov*/, 7, 3)
        
        if (noDst) return dtm;
        
        switch (timezone) {
            case "America/Phoenix":
                // todo: other timezones without dst    
                break;
            default:
                if (inDst(dtm)) {
                    dtm.setHours(dtm.getHours() - 1);
                }
        }
        return dtm;
    }

    function todayAtTimezone(time, timezone) {
      return parseAsTimezone(todateAtTime(time), timezone);
    }

    // Phoenix same as Denver
    console.log(parseAsTimezone('2021-01-01T15:00:00','America/Los_Angeles').toJSON());
    console.log(parseAsTimezone('2021-01-01T15:00:00','America/Denver').toJSON());
    console.log(parseAsTimezone('2021-01-01T15:00:00','America/Phoenix').toJSON());


    // Phoenix same as LA
    console.log(parseAsTimezone('2021-05-01T15:00:00','America/Los_Angeles').toJSON());
    console.log(parseAsTimezone('2021-05-01T15:00:00','America/Denver').toJSON());
    console.log(parseAsTimezone('2021-05-01T15:00:00','America/Phoenix').toJSON());

    // Getting the Time set for a give IATA timezone TODAY
    console.log(todayAtTimezone('15:00', 'America/Los_Angeles').toJSON())
    console.log(todayAtTimezone('15:00', 'America/Denver').toJSON())
    console.log(todayAtTimezone(‘15:00', 'America/Phoenix').toJSON())