Yes, you can. Log into your Billetto account and find your event in "Calendar" at the top-left panel. Select from the drop down box on the right to locate the applicable category (e.g. if your event is completed, select 'My events - Completed'). You will then see a list of your events as defined by this category, 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 hit 'Publish'.
Hint: It might also be an idea to update your new event's URL, you can do this by clicking on the blue link just beneath the title of your event 'Event URL'. If you do not do this, then Billetto will automatically generate a unique URL for your cloned event, which will consist of your original event's URL followed by a random assortment of digits.