Asking user timezone

asking-user-timezone.js

const dateValue = dateInput.value; // Notice that we are grabbing the raw value, not the date value
const userSpecifiedTimezone = "EDT"; // Assume, this was selected by the user

// The date value is now a string, so grab the pieces
const dateParts = dateValue.split("-");
const year = dateParts[0];
const month = dateParts[1];
const day = dateParts[2];

// Construct a new JS date using the individual pieces and timezone specification
const dateWithTimezone = new Date(
  year + "-" + month + "-" + day + " " + userSpecifiedTimezone
);

// Use the 'localized' Date methods to get the new date values
const convertedYear = dateWithTimezone.getFullYear();
const convertedMonth = dateWithTimezone.getMonth() + 1; // Month is zero-indexed
const convertedDay = dateWithTimezone.getDate();

// Format it however you want
document.querySelector("#string-val").innerHTML =
  convertedYear +
  "-" +
  convertedMonth +
  "-" +
  convertedDay +
  " (year-month-day)";
};