sou pm após o tempo em html
var inputEle = document.getElementById('timeInput');
function onTimeChange() {
var timeSplit = inputEle.value.split(':'),
hours,
minutes,
meridian;
hours = timeSplit[0];
minutes = timeSplit[1];
if (hours > 12) {
meridian = 'PM';
hours -= 12;
} else if (hours < 12) {
meridian = 'AM';
if (hours == 0) {
hours = 12;
}
} else {
meridian = 'PM';
}
alert(hours + ':' + minutes + ' ' + meridian);
}
Mohan Eswar