MySQL has three date types for use in columns. These are DATETIME, DATE, and TIMESTAMP.

DATETIME columns store date and time as a string in the form YYYY-MM-DD HH:MM:SS (e.g. 2019-12-25 13:43:15).
DATE columns use just the date part of this format : YYYY-MM-DD (e.g. 2006-12-25).
TIMESTAMP columns, despite their name, are nothing like the unix timestamps used in PHP. A TIMESTAMP column is simply a DATETIME column that automatically updates to the current time every time the contents of that record are altered.

Supposing you have a string in this format 2019-02-25 13:43:15 or DATETIME in var $hari. You can convert it to a newformat like so.

$time = strtotime($hari);
$newformat = date('Y-m-d',$time);
echo $newformat;
// 2019-02-25

The strtotime() function converts to unix timestamp.

Or if already in string format $lahir.

$newformat = date('j F Y', strtotime($lahir));
echo $newformat;
// 25 February 2019

If you want to add an extra day.

$tomorrow = date('Y-m-d H:i:s', strtotime($newformat. ' +1 day'));

In MySQL, sometimes you may encounter this Incorrect datetime value error when you use sql query. Instead of strtotime in PHP, you use STR_TO_DATE. The code looks like this.

UPDATE `resume` SET `ctime` = '0000-00-00 00:00:00' # error
UPDATE `resume` SET `ctime` = STR_TO_DATE("0000-00-00 00:00:00", "%m-%d-%Y %H:%i:%s")

In some cases your MySQL is running on STRICT_MODE so it won't work. You still have to give a real date. So give it a fake one.

UPDATE `resume` SET `ctime` = '2023-01-01' #will work even in datetime