Resets the database cache of date formats and saves all new date formats.
function system_date_formats_rebuild() {
drupal_static_reset('system_get_date_formats');
$date_formats = system_get_date_formats(NULL);
foreach ($date_formats as $type => $formats) {
foreach ($formats as $format => $info) {
system_date_format_save($info);
}
}
// Rebuild configured date formats locale list.
drupal_static_reset('system_date_format_locale');
system_date_format_locale();
_system_date_formats_build();
}