JavaScript date formatting function fails in Zapier with getFullYear error

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1

I’m having trouble with a date formatting function that works fine in my local development environment but throws an error when I run it in Zapier. The error message says TypeError: dateobj.getFullYear is not a function, which suggests the input isn’t being recognized as a proper Date object.

Here’s my current code:

function formatDateTime(inputDate, pattern) {
  var yr = inputDate.getFullYear();
  var mon = ("0" + (inputDate.getMonth() + 1)).slice(-2);
  var day = ("0" + inputDate.getDate()).slice(-2);
  var hr = ("0" + inputDate.getHours()).slice(-2);
  var min = ("0" + inputDate.getMinutes()).slice(-2);
  var sec = ("0" + inputDate.getSeconds()).slice(-2);
  var dayIndex = inputDate.getDay();
  var monthNames = ["JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"];
  var dayNames = ["SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT"];
  var result = "";

  switch(pattern) {
    case "YYYY-MM-DD":
      result = yr + "-" + mon + "-" + day;
      break;
    case "YYYY-MMM-DD DDD":
      result = yr + "-" + monthNames[parseInt(mon) - 1] + "-" + day + " " + dayNames[parseInt(dayIndex)];
      break;
  }

  return result;
}

var dateInput = input.VIP_2bParsed;
var formatPattern = "YYYY-MMM-DD DDD";
var formattedResult = formatDateTime(dateInput, formatPattern);

output = {formattedResult: formattedResult};

What could be causing this issue in Zapier specifically? Do I need to convert the input to a Date object first?

2

This happens because Zapier sends date values as ISO strings or timestamps, not actual Date objects. I ran into the same issue last year building automation workflows. Your function expects a Date object but gets a string - that’s why getFullYear throws an error. Add validation before calling formatDateTime. Use instanceof Date to check if it’s already a Date object. If not, convert it with new Date(dateInput). Watch out for invalid date strings though - they’ll create an Invalid Date object that still won’t work. Add if (isNaN(dateInput.getTime())) after conversion to catch cases where Zapier sends broken date data.

3

Had this exact problem with Zapier and third-party APIs. Zapier’s data transformation between steps is the culprit - sometimes dates come through as Unix timestamps instead of ISO strings, which makes everything messy. I built a more robust date parser that handles multiple formats. Add a preprocessing step that detects the input type first. If it’s numeric (timestamp), use new Date(parseInt(dateInput)). For strings, new Date(dateInput) works fine. Watch out for timezone differences too - some Zapier integrations send dates in different timezone formats depending on your data source.

4

yeah, zapier sends dates as strings by default. just wrap it in new Date() like var dateInput = new Date(input.VIP_2bParsed); before calling the function. that’ll fix it!