Infinite loop in Recurrence.GetNumberOfYearsBetween() with the Japanese calendar in Exchange Server 2019 and 2016

Applies to: Exchange Server 2019Exchange Server 2016


When there's a recurring calendar item based on Japanese Lunar calendar, Recurrence.GetNumberOfYearsBetween() can go into an infinite loop in Microsoft Exchange Server 2019 or Exchange Server 2016. This saturates CPU and makes EWS unusable for all users.


To fix this issue, install one of the following updates:


Learn about the terminology that Microsoft uses to describe software updates.