Deadline won't be saved as null

i’m here again with another problem :frowning_face:
i want to allow user to add their task deadline, it works fine until user open the other task on lightbox, even the deadline it’s not being set before, it keeps showing this
and even after click the remove button, the deadline will be saved as 1899-11-30 on the database
Help me, i don’t know what to do

Hello Farroh,
It might happen if you parse the deadline date incorrectly in the onTaskLoading event handler. You need to make sure that the date format is correct:

gantt.attachEvent("onTaskLoading", function (task) {
  if (task.deadline)
    task.deadline =, "xml_date");
  return true;

It is hard to suggest what else might be wrong as I couldn’t reproduce the issue locally and I don’t see your code.
Here is a working sample:

If that doesn’t help you, please reproduce the issue in the snippet, then click on the “Share” button and send me the link.