How to set TimeZone thru API?

You can update this via the update extension settings API:

PUT /restapi/v1.0/account/~/extension/~ {     "regionalSettings": {         "timezone": {             "id": 58         }     } }

You can get the supported timezone ids from the timezone endpoint:

GET /restapi/v1.0/dictionary/timezone

I have a post with some more information on how to do this here:

https://stackoverflow.com/questions/51681789/is-it-possible-to-set-a-users-ringcentral-timezone-thro...