For any user to share their TimeZone with an external entity, they would have to modify the visibility of timezone/location to "Anyone" or their organization - for Managed Accounts.

DOC: https://support.atlassian.com/atlassian-account/docs/update-your-profile-and-visibility-settings/

For your profile photo, location, local time, and email address, you can choose one of the following settings:

• Anyone - The information in this field is visible to anyone who can view your content, and it is accessible by apps installed in Atlassian cloud products.