Product releases go live in production environments the first Monday of every month, with the exception of when that day falls on a holiday. In the event of a holiday, the release will go out on that Tuesday unless otherwise communicated.
Updates to functionality will be available in your test environment as soon as the functionality is QA and UAT passed. At the time the functionality is available in your test environment, it will be noted on the upcoming month's release notes. Release notes for each month can be found here.
In addition, email communication will go out for all functionality that is considered a major update and/or is considered critical to all customers' process. For non-major or non-critical updates, please review the release notes for the upcoming month to ensure you are aware of changes.