- date_create: documentation ( source)
- timezone_open: documentation ( source)
- date_format: documentation ( source)
- date_timezone_set: documentation ( source)
<?php
$date=date_create("2018-02-20 06:54:57");
echo date_format($date,"Y-m-d H:i:s");
echo "\n";
$tz=timezone_open("Asia/Kolkata");
date_timezone_set($date, $tz);
echo date_format($date,"Y-m-d H:i:s");