Admins can access the calendar settings screen by going to the Calendar icon in the left-hand bar and then to the 'Settings' tab like this...
Here you can specify the time format and the first day of the week.
You can also set a default subject line, description and location with Zendesk placeholders. While the subject line will be seen on the calendar event in Zendesk, the description and location will only be used if you have your calendar integrated with Google Calendar or Office 365. For more information on using placeholders have a look at this article: https://sweethawk.zendesk.com/hc/en-us/articles/219042858
For example, if you'd like to set the default location of an event to the requester's address, first you'll need to create a Zendesk user field. (See this article for more information on creating Zendesk user fields.)
Then add this placeholder {{ticket.requester.custom_fields.address}} into the location mapping field.
The address part of the placeholder {{ticket.requester.custom_fields.address}} needs to be set to the user field key which is defined by you when you create the custom user field. So if you've named your user field something other than "Address", you'll need to make sure you're using the correct field key.