Set date input field's max date to today

You will need Javascript to do this:

HTML

<input id="datefield" type='date' min='1899-01-01' max='2000-13-13'></input>

JS

var today = new Date();
var dd = today.getDate();
var mm = today.getMonth() + 1; //January is 0!
var yyyy = today.getFullYear();

if (dd < 10) {
   dd = '0' + dd;
}

if (mm < 10) {
   mm = '0' + mm;
} 
    
today = yyyy + '-' + mm + '-' + dd;
document.getElementById("datefield").setAttribute("max", today);

JSFiddle demo

JavaScript only simple solution

datePickerId.max = new Date().toISOString().split("T")[0];

<input type="date" id="datePickerId" />

// below trick also works! Thanks jymbob for the comment.
datePickerId.max = new Date().toLocaleDateString('en-ca')

In lieu of Javascript, a shorter PHP-based solution could be:

 <input type="date" name="date1" max="<?= date('Y-m-d'); ?>">

Javascript will be required; for example:

$(function(){
    $('[type="date"]').prop('max', function(){
        return new Date().toJSON().split('T')[0];
    });
});

JSFiddle demo