Invalid start_date argument for calculateEndDate method


I’m updating my app from version 7 to version 7.1.6 (enterprise), after the upgrade I get this error (screenshot) and an empty gantt.

With same data on version 7 all works as expected.

Using Gantt with Angular 12.0.2 and Angular Material.


Hello Andrea,
I suppose you load a task with the start_date parameter that has the null value and no other date parameters.
You should get the same error in the older versions. Here is an example with the 5.2 version:

It might occur because of something else, but it is hard to suggest what might be wrong as I don’t see your code.
Please, add your configuration in the following snippet and make sure that the issue is reproduced there:
Then, click on the Share button and send me the link.
Or send me a ready demo with all the necessary Javascript and CSS files so that I can reproduce the issue locally.


cannot reproduce on snippets site, have a complex json with some inner html templates and the online parser crashes.

I’m using ngrx in my project so data must be immutable, but the gantt alters the received gantt data object adding new props for the tasks (not exactly a parse semantics)

I found a workaround, passing a deep cloned data object works fine.
I can confirm it’s something changed from version 7.0.


Hello Andrea,
Yes, by default, Gantt modifies the provided data. At some point, that was changed (Gantt deep cloned it) after a request, but due to complaints and performance decrease, that was changed back.
In the 7.1 version, the dev team added a way to control that with the deepcopy_on_parse parameter:
You can check how it works in the following snippet:


I had the same error and I found some combinations of plugins can be the cause. ( in my case commenting out keyboard_navigation and overlay resolved the errors)

      grouping: true,
      // keyboard_navigation: true,
      quick_info: true,
      tooltip: true,
      marker: true,
      // overlay: true,
      auto_scheduling: true,


Hello Daisuke,
The issue should be related to the Gantt configuration because the extensions themselves don’t have the issue with the dates: