Follow this checklist:
1. Change the information in Stager and possibly change all impacted variables (start production and end of production, working times etc).
2. Change the information in the Facebook event.
3. Change the information on the Website (date or place of the event itself and in the end of the text/page in the information section).
4. Check on Stager if there are any tickets sold. If that is the case, send an email (all mail recipients in BCC!) and the infom the ticket holders of the change. You get the mail addresses in stager in 'tickets'; 'ticket management'. Click on the name of the person that bought the ticket and you will get all the contact information.
5. Let your colleagues involved in the event know about the change.