Need to give cell value when mail has been sent with time and date in google script code [duplicate] - datetime

Question

I want to give last cell value of col no. 20 when mail has been sent with time and date in the below script. and using this code when more than one rows are added at a time then "sent" value is being added to the last row only and remaining rows are left blank. when new other row is added since value is not equal to sent those values are also been attached So, when mail sent complete column need to be given value as sent. Once please check this
function sendEmail() {
//setup function
var ActiveSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet2");
var StartRow = 2;
var RowRange = ActiveSheet.getLastRow() - StartRow + 1;
var WholeRange = ActiveSheet.getRange(StartRow,1,RowRange,16);
var AllValues = WholeRange.getValues();
var message = "";
//iterate loop
for (i in AllValues) {
//set current row
var CurrentRow = AllValues[i];
//define column to check if sent (starts from "0" not "1")
var EmailSent = CurrentRow[14];
var caseworker = CurrentRow[7];
//if row has been sent, then continue to next iteration
if (EmailSent == "sent")
continue;
//set HTML template for information
message +=
"<p><b>Bank: </b>" + CurrentRow[1] + "</p>" +
"<p><b>Branch: </b>" + CurrentRow[2] + "</p>" +
"<p><b>Region: </b>" + CurrentRow[3] + "</p>" +
"<p><b>Lan Number: </b>" + CurrentRow[4] + "</p>" +
"<p><b>Customer Name: </b>" + CurrentRow[5] + "</p>" +
"<p><b>Loan Type: </b>" + CurrentRow[6] + "</p>" +
"<p><b>Case Worker: </b>" + CurrentRow[7] + "</p>" +
"<p><b>Site Visit Status: </b>" + CurrentRow[8] + "</p>" +
"<p><b>Site Visit Done By: </b>" + CurrentRow[9] + "</p>" +
"<p><b>Document recieved: </b>" + CurrentRow[11] + "</p>" +
"<p><b>File Upload: </b>" + CurrentRow[12] + "</p>" +
"<p><b>Remarks: </b>" + CurrentRow[10] + "</p><br><br>";
//set the row to look at
var setRow = parseInt(i) + StartRow;
//mark row as "sent"
ActiveSheet.getRange(setRow, 15).setValue("sent");
}
//define who to send grants to
var SendTo = "########gmail.com" + "," + "##########gmail.com" + "," + " ##########gmail.com";
//set subject line
var Subject = "New case initiated to Shirisha";
//send the actual email
MailApp.sendEmail({
to: SendTo,
cc: "##########gmail.com",
subject: Subject,
htmlBody: message,
});
}