See the current start date and end date
To shift your project from the date you want, you must go to the project’s setting, by clicking on the gear icon 
In the “Project” section, you can see the start and end date of the project’s planning:

Move the entire planning in one click
To shift your project, change only the start or end date of the project. The tasks will be moved according to the dates chosen. Your confirmation will be requiered.