freebusy

Freebusy refers to information about a calendar user’s availability, specifically the times when they are free or busy. It is used by scheduling systems to find suitable meeting times and to avoid conflicts, without necessarily revealing all event details.

In standard calendar formats, free/busy data is formalized through a component and properties that are designed for interoperability. The iCalendar specification defines a VFREEBUSY component that conveys free and busy time information for a calendar user. Within this component, the FREEBUSY property lists one or more time intervals that indicate periods when the user is busy (and implicitly when they are free outside those intervals). These intervals are typically represented as PERIOD values, consisting of a start time and either an end time or a duration. Time values are usually expressed in UTC or with explicit time zone information to ensure correct cross-time-zone interpretation. A VFREEBUSY object may also include metadata such as the organizer, timestamp, and method of the data exchange.

Freebusy data is exchanged and consumed by scheduling protocols and services, including iTIP, CalDAV, and various calendar clients, to support availability checks and meeting proposals. It enables users to propose times that fit within others’ availabilities while minimizing disclosure of full event details. Privacy considerations are important, since free/busy information can reveal patterns about a person’s schedule; access controls and data minimization practices are commonly applied.