This is useful for tasks that haven’t started yet – you don’t want to change the start date of tasks that have already started.

You can move task start dates by 1) selecting the tasks to move and 2) choosing TASK > Move > Move Task Forward. You will see multiple options, do and undo will help choose between them.

This is more tedious and if dates change again you need to do it again. 

You can select individual tasks, click TASK > Split command and create a split by dragging the bar for individual tasks in the Gantt chart. 

 Easiest to apply and you can edit dates easily again if required.

Add an exception to the working time.

In PROJECT > Working Time, under the thumbnail calendar choose the Exceptions tab and create a new exception called ‘Covid-19’ with start and end dates during which this is going to be nonworking time.

If you have additional custom calendars, make sure to add exceptions to all the calendars that require them.

Fastest but check carefully what adjustments Project has made for you. 

Let Project adjust the plan for you automatically. Click PROJECT > Update Project > select the option Reschedule uncompleted work… You can apply it to all uncompleted tasks or just the ones you select (tick the option of your choice).