Update Teams mobile app by October or lose your calendar

Microsoft has tightened the deadline for users to update their Teams mobile app to avoid losing access to their calendar. Previously set for late October, the deadline has been moved to the beginning of October, giving users only until the end of September to install the update. This change only affects iOS and Android versions; the web and desktop versions remain unaffected.

Those using automatic updates will likely receive a compatible version without any action required. However, managed devices present a different scenario, and administrators must ensure an updated Teams app is deployed.

Microsoft sternly warns that using older versions of the app will result in the loss of calendar access. The company is pushing for a more reliable calendar experience on iOS and Android devices and ensuring compatibility with ongoing Teams service updates. Microsoft announced that it will begin disabling Exchange Web Services (EWS) in Exchange Online on October 1, 2026, a date that was brought forward from the previous deadline.

EWS, which has been in use since 2007, was announced for retirement in 2023 and detailed shutdown process earlier this year. EWS allows applications to access mailboxes and other data in Exchange, but Microsoft is keen to retire it due to its association with intrusions like the Midnight Blizzard incident. Administrators can temporarily re-enable the service through a policy setting, but Microsoft will permanently retire the service in Exchange Online by next year, with no exceptions beyond April 2027.