Microsoft Teams mobile app users on iOS and Android must update their software by late October 2026 [1] to maintain calendar functionality.
This requirement affects global users who rely on the mobile application for scheduling. Failure to update will result in a loss of calendar sync, potentially disrupting professional workflows and meeting management for those who do not use automatic updates.
The loss of access occurs because Microsoft is retiring support for Exchange Web Services (EWS) [1], [3]. Older versions of the Teams mobile app rely on this legacy service to synchronize calendar data. Once EWS is retired, those outdated app versions will no longer be able to communicate with the server to retrieve or update schedule information [1], [3].
Users who have not yet installed the latest version of the app are warned they will lose this access in weeks [2]. The company said users worldwide should ensure their devices are running the most current version of the software to avoid a calendar blackout [3].
This transition is part of a broader shift away from older synchronization protocols. While the core chat and calling features of the mobile app may remain operational, the specific integration with the calendar requires the newer API standards implemented in recent app updates [1], [3].
Administrators and individual users are encouraged to check their app store for pending updates immediately. The deadline remains late October 2026 [1], [3], after which the legacy EWS connection will be severed entirely.
“Users must update the Teams mobile app or they will lose access to calendar functionality.”
This move signals Microsoft's continued effort to phase out legacy infrastructure in favor of more modern, efficient APIs. By retiring Exchange Web Services, the company reduces the technical debt of maintaining multiple synchronization methods, though it creates a hard deadline for users on older hardware or those with disabled automatic updates who may find their devices suddenly incompatible with essential scheduling tools.
