I found that the log of "recent events" (
https://www.eventbrite.co.nz/account-settings/webhooks/xxxxxx) for webhooks are in
PST, not UTC as the 'Z' in the ISO 8601 formatted date would suggest (eg "2021-01-17T20:00:11Z" actually occurred at
2021-01-18 04:00:11 UTC). The account is set to New Zealand, so this is not my local timezone either, and makes conversion harder. I consider this a bug.
Also slightly frustrating is the fact that webhooks cannot be edited, if we want to change the URL or actions, we have to create a new webhook and delete the old one.