<input type="text" value="<?php if(empty($_GET["ts"])) { echo time(); }else{ echo $_GET["ts"]; } ?>" size="10" name="ts" id="ts">
<input type="submit" value="OK" name="submit" onclick="javascript:location.href='?ts=' + document.getElementById('ts').value;">

<?php
if(isset($_GET["ts"])) {
    echo "<hr><br /><b>Timestamp:</b><br />";
    echo date("d.m.Y H:i:s", $_GET["ts"]);
    echo "<br /><br /><b>Datum fällig in:</b><br />";
    if(time() > $_GET["ts"]) {
        echo time2str(time() - $_GET["ts"]);
    }else{
        echo time2str($_GET["ts"] - time());
    }
}

function time2str($time, $anz=9) {
$str="";
if($time>(60*60*24) && $anz > 0) {
$anz--;
$days=floor($time/(60*60*24));
if ($days == "1") { $str.=$days." Tag "; }else{ $str.=$days." Tage "; }
$time=$time-((60*60*24)*$days);
}
if($time>(60*60) && $anz > 0) {
$anz--;
$stunden=floor($time/(60*60));
if ($stunden == "1") { $str.=$stunden." Stunde "; }else{ $str.=$stunden." Stunden "; }
$time=$time-((60*60)*$stunden);
}
if($time>(60) && $anz > 0) {
$anz--;
$min=floor($time/(60));
if ($min == "1") { $str.=$min." Minute "; }else{ $str.=$min." Minuten "; }
$time=$time-((60)*$min);
}
if($time>1 && $anz > 0){
$anz--;
if ($time == "1") { $str.=$time." Sekunde"; }else{ $str.=$time." Sekunden"; }
}
return $str;
}
?>