JavaScript setUTCDate 函数用于根据通用时间设置给定日期的月份中的某一天。setUTCDate Date 函数的语法是：
Date.setUTCDate(Day_Number)
我们使用此 setUTCDate 函数将当前日期根据通用时间设置为 30 号。
<!DOCTYPE html>
<html>
<head>
<title> JS </title>
</head>
<body>
<h1> Example </h1>
<script>
var dt = Date();
document.write("Date and Time : " + dt + "<br/>");
dt.setUTCDate (30);
document.write("After : " + dt);
</script>
</body>
</html>
Example
Date and Time: Thu Nov 08 2018 12:40:51 GMT+0530 (Indian Standard Time)
After : Fri Nov 30 2018 12:40:51 GMT+0530 (Indian Standard Time)在此 JavaScript 示例中，我们根据通用时间 UTC 将自定义日期的日期设置为 31 号。
<!DOCTYPE html>
<html>
<head>
<title> JavaScriptSetUTCDateFunctions </title>
</head>
<body>
<h1> JavaScriptsetUTCDateFunctionExample </h1>
<script>
var dt = Date("January 1, 2017 10:11:19");
document.write("Date and Time : " + dt + "<br/>");
dt.setUTCDate (31);
document.write("After setUTCDate () : " + dt);
</script>
</body>
</html>
如果我们将月份数字设置为大于 31 的值，setUTCDate 将进入下个月。
<!DOCTYPE html>
<html>
<head>
<title> JS </title>
</head>
<body>
<h1> Example </h1>
<script>
var dt = Date("January 1, 2017 10:11:19");
document.write("Date and Time : " + dt + "<br/>");
dt.setUTCDate (35);
document.write("After : " + dt);
</script>
</body>
</html>
Example
Date and Time: Sun Jan 01 2017 10:11:19 GMT+0530 (Indian Standard Time)
After : Sat feb 04 2017 10:11:19 GMT+0530 (Indian Standard Time)