Abstract: Systems and methods for inferring and notifying an end user about reduced availability of a target user or group of target users in a time range of interest. For instance, the reduced availability service includes components for collecting calendar event information and calendar settings information corresponding to a calendar of a target user, generating an interval graph data structure based on the collected calendar information, determining working hours for the target user, identifying periods of time where reduced availability is determined in the target user's calendar, and generating a notification of the target user's reduced availability for alerting the end user.