Convert UNIX timestamp to date time (javascript)

You have to multiply by 1000 as JavaScript counts in milliseconds since epoch (which is 01/01/1970), not seconds :

var d = new Date(timestamp*1000);

Reference

function convertTimestamp(timestamp) {
    var d = new Date(timestamp * 1000), // Convert the passed timestamp to milliseconds
        yyyy = d.getFullYear(),
        mm = ('0' + (d.getMonth() + 1)).slice(-2),  // Months are zero based. Add leading 0.
        dd = ('0' + d.getDate()).slice(-2),         // Add leading 0.
        hh = d.getHours(),
        h = hh,
        min = ('0' + d.getMinutes()).slice(-2),     // Add leading 0.
        ampm = 'AM',
        time;

    if (hh > 12) {
        h = hh - 12;
        ampm = 'PM';
    } else if (hh === 12) {
        h = 12;
        ampm = 'PM';
    } else if (hh == 0) {
        h = 12;
    }

    // ie: 2014-03-24, 3:00 PM
    time = yyyy + '-' + mm + '-' + dd + ', ' + h + ':' + min + ' ' + ampm;
    return time;
}

You can get the value by calling like convertTimestamp('1395660658')

Because your time is in seconds. Javascript requires it to be in milliseconds since epoch. Multiply it by 1000 and it should be what you want.

//time in seconds
var timeInSeconds = ~(new Date).getTime();
//invalid time
console.log(new Date(timeInSeconds));
//valid time
console.log(new Date(timeInSeconds*1000));

const timeStamp = 1611214867768;

const dateVal = new Date(timeStamp).toLocaleDateString('en-US');
console.log(dateVal)