Get human readable time string for an hour from current time (with optional offset).

oneHourFromNow.js

const oneHourFromNow = (() => {
  const pad = num => `0${num}`.slice(-2);
  const parse = num => Math.max(~~parseFloat(num), 0);
  const meridian = hour => ["AM", "PM"][+(hour >= 12)];
  const tomorrow = date => date.getDate() > new Date().getDate();
  const timezone = date => `GMT+${-(date.getTimezoneOffset() / 60)}`
    // .replace(/\+?([-+])/, "$1");
    .replace(/\+?([-+])(\d+)/, (_, $1, $2) => +$2 ? `${$1}${$2}` : "");

  return (offset) => {
    const date = new Date(Date.now() + (3600 - parse(offset)) * 1000);
    const minute = date.getMinutes();
    const hour = date.getHours();

    return `${tomorrow(date) ? "tomorrow" : "today"} by ${[
      pad(hour > 12 ? hour % 12 : hour),
      pad(minute)
    ].join(":")} ${meridian(hour)} (${timezone(date)})`;
  };
})();