Create Calendar event times from spreadsheet data for multiple time zones - google-apps-script

Question

I have created a basic Google sheet where staff will log meetings and then be able to export them to the google calendar.
The problem is that I have staff based in the US and in different timezones. I tried changing the spreadsheet settings but the timezones in Google seem a little unreliable (Pacific Time showing as GMT-8 when it is currently -7)...
I tried hardcoding the time difference as follows:
var tstart = new Date(tstart1.getTime() + 420 * 60000)
Now this works, except when it pushes the time past midnight. At this point it gets confused and states that end time must be later than start time. I guess therefore it is not pushing the date forward.
How can I stop this error occurring?
The rest of the code:
function onOpen() {
var sheet = SpreadsheetApp.getActiveSpreadsheet();
var entries = [{
name : "Export Events",
functionName : "exportEvents"
}];
sheet.addMenu("Calendar Actions", entries);
};
/**
* Export events from spreadsheet to calendar
*/
function exportEvents() {
var sheet = SpreadsheetApp.getActiveSheet();
var headerRows = 1; // Number of rows of header info (to skip)
var range = sheet.getDataRange();
var data = range.getValues();
// var calId = sheet.getRange("H2:H2").getValue();
var calId = "********";
var cal = CalendarApp.getCalendarById(calId);
for (i=0; i<data.length; i++) {
if (i < headerRows) continue; // Skip header row(s)
var row = data[i];
var date = new Date(row[1]); // First column
var title = row[2]; // Second column
var initial = row[0];
var city = row[3];
var concatTitle = initial + " - " + title + ", " + city;
var tstart1 = new Date(row[4]);
var tstart = new Date(tstart1.getTime() + 420 * 60000)
tstart.setDate(date.getDate());
tstart.setMonth(date.getMonth());
tstart.setYear(date.getYear());
//var tstop = new Date(row[4]);
var tstop = new Date(tstart.getTime() + row[5] * 60000);
// Logger.log(new Date(tstart.getTime() + 65 * 60000))
// var tstop = new Date(tstart + row[4]);
tstop.setDate(date.getDate());
tstop.setMonth(date.getMonth());
tstop.setYear(date.getYear());
var loc = row[6];
var desc = row[7];
var id = row[8]; // Sixth column == eventId
// Check if event already exists, update it if it does
try {
var event = cal.getEventSeriesById(id);
}
catch (e) {
// do nothing - we just want to avoid the exception when event doesn't exist
}
if (!event) {
//cal.createEvent(title, new Date("March 3, 2010 08:00:00"), new Date("March 3, 2010 09:00:00"), {description:desc,location:loc});
var newEvent = cal.createEvent(concatTitle, tstart, tstop, {description:desc,location:loc}).getId();
row[8] = newEvent; // Update the data array with event ID
}
else {
event.setTitle(concatTitle);
event.setDescription(desc);
event.setLocation(loc);
// event.setTime(tstart, tstop); // cannot setTime on eventSeries.
// ... but we CAN set recurrence!
var recurrence = CalendarApp.newRecurrence().addDailyRule().times(1);
event.setRecurrence(recurrence, tstart, tstop);
}
debugger;
}
// Record all event IDs to spreadsheet
range.setValues(data);
}