$filename = 'd:\\data.txt';
// Time remain the same, only the date is modified
if (touch($filename, mktime(date("H", filemtime($filename)),
date("i", filemtime($filename)),
date("s", filemtime($filename)),
12, 31, 1999)))
echo "$filename date & time: ".date("m/d/Y H:i:s", filemtime($filename));
else
echo "Error <br />";
/*
run:
d:\data.txt date & time: 12/31/1999 18:53:14
*/