Open global.php and locate this code:
//-----------------------------------------------------
//--- Generate Setting --------------------------------
//-----------------------------------------------------
$sql = "SELECT setting_name, setting_value
FROM ".SETTINGS_TABLE;
$result = $site_db->query($sql);
if (!$result) {
echo $lang['no_settings'];
exit;
}
while ($row = $site_db->fetch_array($result)) {
$config[$row['setting_name']] = $row['setting_value'];
}
$site_db->free_result();
Add after it:
$hour = date("G");
if( $hour > 7 && $hour <= 20 )
$config['template_dir'] = "day_template";
else
$config['template_dir'] = "night_template";
Where day_template is the name of the template directory that holds your daytime template, etc.