Question

I am trying to write a custom function that takes two cell ranges (Start time and Stop time) as input and then outputs the total hours. If the cells are formatted as normal numbers (i.e. 9:00pm is represented as 0.875) the function works fine. If I format the cells as time the cell value the formula is in says “#NUM!” and the tooltip is “error: Overflow”. Is there a way to read the raw cell data without the formatting so that my formula will work?

Formula code

function getHoursTest(startRange, stopRange) {
  var hours = 0; // define "hours" with start value of 0
  var i = startRange.length - 1;  // define "i" and assign the position of the last array element

  while(i>=0){
        hours = hours + ((stopRange[i] - startRange[i])*24);
        i--
  }
  return hours;
}

Answer 1

When a cell is formatted as a date or time value then it’s value is passed to Apps Script as a JavaScript Date object. You can determine if the value is a date by using code like:

if (value instanceof Date) {
  ...
} else {
  ...
}