[Logician]

There are some issues to be solved like if your style will overwrite forum's forced styles or user's custom style but assuming answers are no for both here is your code:

edit global.php (in forum dir, not in Admin dir!), find:

PHP Code:

// is style in the forum/thread set?
if (isset($codestyleid) and $codestyleid!=0) {
  $styleid=$codestyleid;
} else {

  // Will look in the user info for a style
  if ($bbuserinfo['styleid']!=0) { //style specified
    $styleid=$bbuserinfo['styleid'];
  } else { //no style
    $styleid=1;
  } 


Replace it as:

PHP Code:

// is style in the forum/thread set?
if (isset($codestyleid) and $codestyleid!=0) {
  $styleid=$codestyleid;
} else {

  // Will look in the user info for a style
  if ($bbuserinfo['styleid']!=0) { //style specified
    $styleid=$bbuserinfo['styleid'];
  } else { //no style
$styleid=date("w",time())+1;
  } 


Now the hack will make these styles default automatically everyday at 12:00 AM (According to the server time!):
Sunday => Style 1
Monday => Style 2
..
..
Saturday => Style 7

Enjoy.. :glasses: