Any confirmed event in Prism can be changed to a new date as long as you have access to both the "Create Holds" and the "Manage Holds" permissions. There are two different methods to do so.
From the Calendar:
Best for quick changes to a show's date within the same month
On the calendar, you can move confirmed events (as well as holds) to new dates by clicking-and-dragging them. This is a convenient way to update dates without leaving the calendar.
From an Event Page:
Best for more long-term date editing, like if a show is postponed more than a few weeks. You will not lose any event data (i.e. offer details, actual costs, notes) when you change the dates of your event.
Go to the event's page
Click on the date in the header
Click on the current date of the show to open the calendar pop-out and unselect it as the show date from the calendar
On the calendar pop-out, navigate to the new date and select the desired date and click Done
Note that if you would like to change your Confirmed event back to Hold when using this method, you must update the status of the event in the dropdown menu before changing the dates.