A presence-based future availability system, including a memory comprising: a future availability program that allows a caller to obtain future availability information about a call recipient if the caller has been designated by the recipient to have access to the future availability data; and a processor coupled to the memory that executes the future availability program; characterized in that the future availability program is devised such that in case it has detected an incoming call of the caller and this caller has been designated by the call recipient to have access to the future availability data, and the call recipient as a presence state thereof having indicated to be unavailable, the future availability program is adapted to allow the caller to select whether to a) access the call recipient's future availability data in order to learn when the call recipient is available to be contacted, and/or b) set a Tell-Me-When action on the call recipient, resulting in a call being placed automatically between the caller and the call recipient, once the change of the presence state of the call recipient triggers the option selected by the caller, and wherein the system further comprises an inference engine located on the memory that stores information about the call recipient, wherein the inference engine is adapted to infer the future availability based upon a call recipient's current presence status, what the call recipient has published in the form of a calendar, and what communication rules the call recipient has configured, wherein the rules take a real-time presence information of other users that have been assigned by the call recipient as delegates, call recipient location and time-zone, device/media capability, and/or calendar context in consideration to determine what options are being offered to the caller and how to deal with the call for further processing/routing, wherein the system is adapted to resolve time differentials between the caller and the call recipient, wherein the system is adapted to convert the future availability data/time information of the call recipient to the caller's time zone. a memory comprising: a future availability program that allows a caller to obtain future availability information about a call recipient if the caller has been designated by the recipient to have access to the future availability data; and a processor coupled to the memory that executes the future availability program; characterized in that the future availability program is devised such that in case it has detected an incoming call of the caller and this caller has been designated by the call recipient to have access to the future availability data, and the call recipient as a presence state thereof having indicated to be unavailable, the future availability program is adapted to allow the caller to select whether to a) access the call recipient's future availability data in order to learn when the call recipient is available to be contacted, and/or b) set a Tell-Me-When action on the call recipient, resulting in a call being placed automatically between the caller and the call recipient, once the change of the presence state of the call recipient triggers the option selected by the caller, a) access the call recipient's future availability data in order to learn when the call recipient is available to be contacted, and/or b) set a Tell-Me-When action on the call recipient, resulting in a call being placed automatically between the caller and the call recipient, once the change of the presence state of the call recipient triggers the option selected by the caller, and wherein the system further comprises an inference engine located on the memory that stores information about the call recipient, wherein the inference engine is adapted to infer the future availability based upon a call recipient's current presence status, what the call recipient has published in the form of a calendar, and what communication rules the call recipient has configured, wherein the rules take a real-time presence information of other users that have been assigned by the call recipient as delegates, call recipient location and time-zone, device/media capability, and/or calendar context in consideration to determine what options are being offered to the caller and how to deal with the call for further processing/routing, wherein the system is adapted to resolve time differentials between the caller and the call recipient, wherein the system is adapted to convert the future availability data/time information of the call recipient to the caller's time zone.