studebaker-time.js

// This function takes a date object as an argument and returns the corresponding offset
// value based on whether daylight saving time (DST) is currently being observed for that date.
// It was from Joel Studebaker but has been modified somewhat.
const dstOffset = (datevar) => {
  // Define a function to calculate the standard timezone offset for a given date.
  Date.prototype.stdTimezoneOffset = function () {
    const jan = new Date(this.getFullYear(), 0, 1);
    const jul = new Date(this.getFullYear(), 6, 1);
    return Math.max(jan.getTimezoneOffset(), jul.getTimezoneOffset());
  };

  // Define a function to check whether DST is currently being observed for a given date.
  Date.prototype.isDstObserved = function () {
    return this.getTimezoneOffset() < this.stdTimezoneOffset();
  };

  // Check if DST is currently being observed for the given date.
  if (datevar.isDstObserved()) {
    if (scriptProperties.getProperty("TIME_DST") === null) {
      Logger.log('No DST Time Zone "TIME_DST" provided, cannot continue.');
      return;
    }

    // Return the DST offset if it is being observed.
    return scriptProperties.getProperty("TIME_DST");
  }

  if (scriptProperties.getProperty("TIME_STANDARD") === null) {
    Logger.log('No Standard Time Zone "TIME_STANDARD" provided, cannot continue.');
    return;
  }

  // Return the standard offset if it is not being observed.
  return scriptProperties.getProperty("TIME_STANDARD");
};