Due Date Server error 500

[jeydee]

After i added
$g_due_date_update_threshold = DEVELOPER;
$g_due_date_view_threshold = REPORTER;

Time picker is displayed correctly but when we use it, after save it display Server error 500. Date max length is set to 16. I couldn't find any easy solution to fix this problem.

We use Mantis BT 1.2.19.

Any idea?