lvovitch,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
</head>
<body>
<input type="text" name="hour" value="23">
<input type="text" name="min" value="55">
<input type="text" name="korr" value="55">
<input name="ok" type="button" value="ok">
<script>
var hour = document.getElementsByName("hour")[0],
min = document.getElementsByName("min")[0],
korr = document.getElementsByName("korr")[0],
ok = document.getElementsByName("ok")[0];
ok.onclick = function ()
{
var date = new Date();
date.setHours(hour.value,((min.value|0)+(korr.value|0)),0,0);
hour.value = date.getHours();
min.value = date.getMinutes();
}
</script>
</body>
</html>