Get times in between two timestamps with JavaScript.

getDates.js

/**
 * Made a few tweaks from Miguel's original code to...
 * meet my usecase.
 */
import dayjs from 'dayjs';
import utc from 'dayjs/plugin/utc';
import customParseFormat from 'dayjs/plugin/customParseFormat';
import timezone from 'dayjs/plugin/timezone';

dayjs.extend(utc);
dayjs.extend(timezone);
dayjs.extend(customParseFormat);

function getAvailabilitySlots(startTime, endTime) {
  const slots = [];
  let start = startTime;
  const addDays = function (minutes) {
    const currentTime = new Date(this.valueOf());
    currentTime.setMinutes(currentTime.getMinutes() + minutes);
    return currentTime;
  };
  while (start <= endTime) {
    slots.push(start);
    start = addDays.call(start, 15);
  }
  return slots;
}

// Usage
const slots = getAvailabilitySlots(
  new Date(new Date().setUTCHours(9, 0, 0, 0)),
  new Date(new Date().setUTCHours(17, 0, 0, 0))
);

slots.forEach(function (date) {
  console.log(dayjs(date).local().format());
});