Yes, you can. Log into your Billetto account and find your event in "Calendar" at top left corner. Select from the side panel to the left which event you wish to duplicate. You will then see a list of your events as defined by the category you have chosen, scroll down to the event you are interested in duplicating and click on the 'Clone event' icon:
You will then be taken to the 'Create/Edit Event' screen, however all of the information from your original event will be pre-populated in all of the information fields. Simply edit these details as required, paying particular attention to the event start/end dates, and the tickets start/end date under 'Advanced settings' and hit 'Publish'.