Depends what you want to do with the data - there's no convenient human readable export format (not sure such a format even exists!). Though you can export an ICS file, which includes all the events in a calendar, that can be imported into another calendar program, which is probably much more useful!

If you go to any calendar on Voice you will see a Subscribe to this calendar button. This is a special link that calendar apps can use to subscribe to all the events. But really it's just a URL like any other.

So for example on this calendar the Subscribe button loads the URL:
webcal://e-voice.org.uk/voiceusers/calendar/ics/all-events.ics

You can use that URL to subscribe to the calendar so that new events are automatically added to your calendar app.

However, if you want to download the ICS file instead of subscribing to it, you can change the webcal: bit of the URL to https: and your browser will (probably) offer to save the file. e.g..,
https://e-voice.org.uk/voiceusers/calendar/ics/all-events.ics

Hope this helps!

Joe