How to pull date from cell and compare it to today's date - date

Question

I am using a spreadsheet to manage certification expiration dates. I want to send an email to an employee when their certification is expiring within 90 days. I only want to send one email. I am struggling getting the date from the cell and comparing it to today's date.
I want to send an email if Todays Date + 90 days in MS is > certification expiration date in MS.
I started using a template to prevent sending duplicate emails. I got it working with if && with words in two cells. I am struggling getting the dates to work. I have tried using getTime() to get the dates in MS but getValues().getTime returns an error.
var EMAIL_SENT = 'EMAIL_SENT';
var NintyDayInMs = 90*24*60*60*100;
var Today = new Date().getTime();
var expired = Today+NintyDayInMs;
/**
* Sends non-duplicate emails with data from the current spreadsheet.
*/
function sendEmails2() {
var sheet = SpreadsheetApp.getActiveSheet();
var startRow = 2; // First row of data to process
var numRows = 2; // Number of rows to process
// Fetch the range of cells A2:B3
var dataRange = sheet.getRange(startRow, 1, numRows, 4);
// Fetch values for each row in the Range.
var data = dataRange.getValues();
for (var i = 0; i < data.length; ++i) {
var row = data[i];
var emailAddress = row[0]; // First column
var message = row[1]; // Second column
var emailSent = row[2]; // Third column
var exp = row[3]; // Fourth column
var expDate = exp.getTime();
if (emailSent != EMAIL_SENT && expDate < expired) { // Prevents
sending duplicates
var subject = 'Sending emails from a Spreadsheet';
MailApp.sendEmail(emailAddress, subject, message);
sheet.getRange(startRow + i, 3).setValue(EMAIL_SENT);
// Make sure the cell is updated right away in case the script is
interrupted
SpreadsheetApp.flush();
}
}
}
My current code results in
TypeError: Cannot find function getTime in object (Date in cell).
(line 26, file "Code")

Answer 1

Read Adding Days to a Date - Google Script for a better understanding of date arithmetic in scripts.
The flaw is in trying to chain the expiry date. Instead of:
var exp = row[3]; // Fourth column
var expDate = exp.getTime();
use just:
var expDate = new Date(row[3]); // make the sheet value a date object
Then the rest goes naturally...
var expDate = new Date(row[3]); // make the sheet value a date object
Logger.log("expiry = "+expDate);
var today = new Date();
Logger.log("today = "+today);
var today90 = new Date(today.getTime()+90*3600000*24);// 90 days from today
Logger.log("today90 = "+today90);
if ((today90 > expDate) && (emailSent!=EMAIL_SENT)){
Logger.log("send the email");
}
else
{
Logger.log("don't send the email");
}