Can I change the start/due date on my card in Gantt chart?

When a card has neither start nor due date, it is different from other cards on Gantt chart in two ways: firstly, it is grayed out on the left; secondly, there is no track bar for this card on the right. 

There’re 2 options to set new or update existing dates:

1) To click on the card in Gantt chart view to open the right panel and set new start/due dates manually in the Card Details section.

2) To set or adjust the start/due date on your card using a track bar. Hover the mouse over the area on the Gantt Chart corresponding to a card, find the date on the timeline you want to be the start date of your card, press the left button of your mouse and lead a cursor to the end date and release the button.

To adjust dates simply click on the left/right edge of the track bar representing the time frame for a particular task and drag it to a particular date. Dates will change automatically. If you have pushed them to your Google Calendar, changes will be displayed there as well.