sectom/functions/londonTime.js

Sectom is a useful npm package that has multiple easy to use functions.

const formatDate = require("../private/formatDate");

/**
 * Finds the time in london for the current date or a provided date
 * @param {Date} d
 * @returns
 */
function getLondonTime(d = undefined) {
  // Use provided date or default to current date and time
  d = d || new Date();

  // Get start and end dates for daylight saving for supplied date's year
  // Set UTC date values and time to 01:00
  var dstS = getLastSunday(d.getFullYear(), 3);
  var dstE = getLastSunday(d.getFullYear(), 10);
  dstS = new Date(
    Date.UTC(dstS.getFullYear(), dstS.getMonth(), dstS.getDate(), 1)
  );
  dstE = new Date(
    Date.UTC(dstE.getFullYear(), dstE.getMonth(), dstE.getDate(), 1)
  );
  // If date is between dstStart and dstEnd, add 1 hour to UTC time
  // and format using +60 offset
  if (d > dstS && d < dstE) {
    d.setUTCHours(d.getUTCHours() + 1);
    return formatDate(d, 60);
  }
  // Otherwise, don't adjust and format with 00 offset
  return formatDate(d).toString();
}

module.exports = getLondonTime;