Change the venue name and address and/or event time under "Event details":
If you have set a specific time for sales end, update this as well under "Ticket types & prices":
If you have set specific date ranges for ticket types, update these as well.
Use "Emails" tool to send a message to your buyers, notifying them about the changes. Select "Include the tickets in an email" to include updated tickets.
If you change the event time, it might be possible that some of your buyers are requesting a refund. Read about refunds and cancelling orders.