Hi Himmat,
Greetings from Syncfusion support.
We have analyzed the code snippets you shared and noticed that you have mapped the duration field in the taskFields. Gantt gives more priority to duration of the tasks when both duration and end date fields are mapped. You have also used manual scheduling mode in your sample. Hence, the duration of the tasks is calculated without considering the weekends and holidays in the timeline. If you wish to render the tasks based only on the end dates provided, please remove the mapping of the duration from your sample.
Regards,
Monisha.