Beginning January 7th, 2019, Google will stop sending SMS notifications for Google Calendar events.
Instead of SMS notifications, users will have to rely on in-app notifications — regardless of their device or connection — or email notifications as the primary method of reminder.
According to a Google blog post, those who received Calendar notifications through SMS will receive event notifications from a web browser with Calendar open, or a mobile device with Calendar installed.
Further, these users will receive an email instead of an SMS notification for new, changed or cancelled events or event responses.
Additionally, Google stated that it would update the Google Calendar API to reflect the change.
Overall, it’s somewhat disappointing that Google is deprecating the SMS notification option. Plenty of people likely relied on that option.