Google spreadsheet: Add days to date set by inputBox, fill range

Question

How do I fill up a range in a Google Spreadsheet based on a startDate that has been set by an inputBox? Basically, (1) User inputs startDate; (2) script fills up cells A1 to A13 starting from startDate and adding 7 days for each row.

Here's what I tried to do:

var startDate = Browser.inputBox('What is the start date?', Browser.Buttons.OK_CANCEL);
for (var k = 0; k < (13); k++) {
  sheet.getRange((k+1),1).setValue(startDate + k * 7);
}

Unfortunately I think setValue treats startDate as a string? So for an input of 15/10/2013 in the box, and cells formatted to dd-mmm-yyyy, the cells are filled up with 15-Oct-20130, 15-Oct-20137, 15-Oct-201314 and so on. What I'd hoped for was 15-Oct-2013, 22-Oct-2013, 29-Oct-2013 and so on. Help?

Answer 1

You could take advantage of UIApp's dedicated widget to choose the starting date and of using spreadsheet formulas to create your date sequence (as you know that =date+7 in spreadsheet gives automatically the date 7 days later.

Here is how it could go :

function dateSequence() {
  var app = UiApp.createApplication().setTitle('Choose a start Date').setHeight('100').setWidth('200');
  var date = app.createDateBox().setName('date').setValue(new Date());
  var clickHandler = app.createServerHandler('setDate').addCallbackElement(date);
  app.add(date).add(app.createButton('submit', clickHandler));
  SpreadsheetApp.getActive().show(app)
}

function setDate(e){
  var app = UiApp.getActiveApplication().close();
  var sheet = SpreadsheetApp.getActiveSheet();
  sheet.getRange(1,1).setValue(e.parameter.date);
  for (var k = 1; k < 13; k++) {
    sheet.getRange((k+1),1).setFormula("= (A"+k+")+"+7);
  }
  return app;
}