Fixing script to input 2021-02-01 instead of 2021-02-32 - datetime

Question

I'm trying to this code in the Script Editor of Google Sheets to insert today's date along with a consistent piece of text, and it was working fine up until Jan 31, 2021, when it started inserting 2021-02-32, 2021-02-33, etc. instead of 2021-02-01, 2021-02-02, etc. Here's the code I'm running:
function daily() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sh = ss.getSheetByName("Social Tracker");
var date = Utilities.formatDate(new Date(), "GMT", "YYYY-MM-DD");
var aValues = sh.getRange("A1:A").getValues();
var aLast = aValues.filter(String).length;
// Assuming A and B have same last row, no need for B
// If different, need to calculate separately
var bValues = sh.getRange("B1:B").getValues();
var bLast = bValues.filter(String).length;
// If A and B are the same, use setValues
sh.getRange(aLast + 1, 1, 1, 2).setValues([[date,'handle']]);
var sheet = SpreadsheetApp.getActiveSheet();
var followers = sheet.getRange(2,5,sheet.getLastRow()).getValues();
var nextRowJ = getFirstEmptyRow('J');
var following = sheet.getRange(2,6,sheet.getLastRow()).getValues();
var nextRowK = getFirstEmptyRow('K');
var engagement = sheet.getRange(2,7,sheet.getLastRow()).getValues();
var nextRowL = getFirstEmptyRow('L');
var likes = sheet.getRange(2,8,sheet.getLastRow()).getValues();
var nextRowM = getFirstEmptyRow('M');
var comments = sheet.getRange(2,9,sheet.getLastRow()).getValues();
var nextRowN = getFirstEmptyRow('N');
var posts = sheet.getRange(2,4,sheet.getLastRow()).getValues();
var nextRowO = getFirstEmptyRow('O');
// Record current balance and timestamp at end of columns B & C
sheet.getRange(nextRowO, 15, 1, 1).setValues([[posts]]);
sheet.getRange(nextRowJ, 10, 1, 1).setValues([[followers]]);
sheet.getRange(nextRowK, 11, 1, 1).setValues([[following]]);
sheet.getRange(nextRowL, 12, 1, 1).setValues([[engagement]]);
sheet.getRange(nextRowM, 13, 1, 1).setValues([[likes]]);
sheet.getRange(nextRowN, 14, 1, 1).setValues([[comments]]);
}
// From https://stackoverflow.com/a/9102463/1677912
function getFirstEmptyRow(columnLetter) {
columnLetter = columnLetter || 'A';
var rangeA1 = columnLetter + ':' + columnLetter;
var spr = SpreadsheetApp.getActiveSpreadsheet();
var column = spr.getRange(rangeA1);
var values = column.getValues(); // get all data in one call
var ct = 0;
while ( values[ct][0] != "" ) {
ct++;
}
And here's an image of the cells that are being filled in by the script. I'm assuming my issue is with the line:
sh.getRange(aLast + 1, 1, 1, 2).setValues([[date,'consistent piece of text']]);
How can I adjust this to make sure it follows the next date in A1, ie. inserts 2021-02-01 instead of 2021-02-32?

Answer 1

Use:
var date = Utilities.formatDate(new Date(), "GMT", "yyyy-MM-dd");
Reason:
Utilities.formatDate(date, timeZone, format) follows this format guidelines
When you use "DD", you specify the Day in a year. If you want to specify the Day of the month you need to use dd
In addition, when you use "YYYY" you are referring to a Week year. If you want to get the actual year use "yyyy" instead.

Answer 2

If you find using Java SE Simple Date Format counterintuitive and you are using Google Apps Script V8 runtime instead of using Utilities.formatdate() you might use to Date.prototype.toLocaleDateString
Instead of "YYYY-MM-DD" use "yyyy-MM-dd"
YYYY stands for 4 digit weak year (the first/last week of the year it might return a number different of what you are expecting.
yyyy stands for 4 digit year
DD stands for day year (32 is February 1st)
MM stands for 2 digit month (02 is February)
mm stats for 2 digit minutes