To modify the start or end date of a schedule item, navigate to the project page and locate the specific item. Click on either the start or end date, and a calendar will appear, allowing you to select the desired date.

On a calendar, it is not possible to select an end date that occurs prior to the start date.

Another method for modifying the dates is by clicking on this icon   and selecting "Edit" from the provided list:

It will open new modal, click on the calendar icon then select the new dates:

Click on the "Save" button for saving changes.

If you are using Gantt chart, just click on the then click on the "Edit" and change the dates from the opened modal:

Another approach to adjusting the dates directly from the Gantt chart is by utilizing the drag and drop feature. Simply click on the schedule item's bar and move it to the desired date. As you drop it, the start and end dates will be automatically adjusted accordingly.