$datatime = new DateTime("now", new DateTimeZone('Asia/Taipei'));
$datatime -> setDate(2020,05,11);
$datatime -> setTime(15,08,51);
$datatime -> format('1'); //Monday
$datatime -> format('Y-m-d h:i:s');
$datatime -> modify('+3 day');
$datatime -> modify('-2 month');
$datatime -> modify('+1 year');
$datatime -> modify('+3 hour');
index.php
<div>輸入不同的日期格式</div><hr>
<form action="use.php" method="post" >
以text型態輸入時間:<input type="text" name="date1"><br/>
以date型態輸入時間:<input type="date" name="date2"><br/>
<input type="submit"> <input type="reset">
</form>
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use.php
<?php //轉換日期格式
date_default_timezone_set('Asia/Taipei');
$date1 = $_POST['date1'];
$date2 = $_POST['date2'];
$dateTime1 = new DateTime($date1);
$dateTime2 = new DateTime($date2);
echo "第1個日期格式為".$date1."<br/>";
echo "第2個日期格式為".$date2."<br/>轉換日期格式如下:<hr>";
echo "第1個日期格式為".$dateTime1->format('Y-m-d h:i:s')."<hr>";
echo "第2個日期格式為".$dateTime2->format('Y-m-d h:i:s')."<hr>";
?>